If you print out the Schematic you can then highlight connections that you make in the circuit.

On Tag strip 2 R12 a 2.2k resistor goes between Node(A) & Node(B) and R13 a 4.7k resistor goes between  Node(A) &  Node(C).
The Schematic is wired different to above picture, either way will work fine.

The rectifier is mounted on Tag strip 3. On the top of the rectifier you will see the markings for - & +, and S & S. The negative leg of the rectifier will go to the pin on the tag strip that bolts to the chassis. The positive leg of the rectifier will go to the pin on the tag strip where   Node(A) connects. The two Sides marked S & S is where we connect the Toroidal transformer secondaries, so connect these two legs of the rectifier to two pins of the tag strip that are beside each other.

Connect the two twelve volt windings from the Toroidal Power Transformer in series by joining the yellow and black wires together.  The red wire will go to the centre pin on the on/off switch and the orange wire will go to the centre pin of the 2.5 mm power jack. To complete the primary circuit the outside pin of the 2.5 mm power jack will connect to the outside pin on the on/off switch.

AC comes out of the two blue wires from the Toroidal Transformer secondaries. At Node(A) where the rectifier connects it is rectified to approx 130 volts DC loaded(tubes in and connected) or (160volts unloaded).

The 3PDT toggle switch on one node switches the power on/off to the power tube and on the other two nodes switches the signal from the preamp to go to the output jack directly or through the power tube and output transformer.  So when the power to the tube is off the signal goes from the preamp to the output jack. The signal comes from the 3PDT into the power tube at pin 2.  The signal from the preamp, (centre pin on the DPDT) is connected to the centre pin on the 3PDT. The bottom pin of this 3PDT pole is connected to pin 2 of the power tube.  On another pole on the 3PDT toggle switch the tip of the output jack is connected to the centre pin, the bottom pin is connected to the yellow wire on the output transformer. The top pins of these two 3PDT nodes are connected together.

The white twisted wires are connected to the Heaters, pins 3 & 4 of the power tube socket and to the centre pin on the on/off switch and the centre pin of the 2.5 mm power jack. Pins 3 & 4 on the power tube are connected to pins 4 & 5 of the preamp tube.    R16 & 17 two 150r resistors connect to the heater pins to form a Virtual centre tap to reduce hum, they could be connected to ground but are connected to the cathode pin on the power tube with the cathode providing an elevated DC Voltage.

Node(B) connects to pin 6 on the Second preamp socket directly and to pin 1 through R23 a 100k resistor. 
A red wire connects pin 7 to pin 1. The signal comes in at pin 2 and the output goes to the tone stack from pin 8.
Node(C) connects to the plates on the First preamp socket through plate load resistors, R3 & R4.

The control grid has a big influence on how much current flows in the 12AX7 Tube,

As the voltage at the grid goes more negative the current through the tube decreases until no current flows and the anode current is cut-off. The grid voltage may continue to swing more negative, the tube will remain in cut-off and the output waveform will be clipped. Depending on the circuit a 12AX7 will cut-off anode current when the grid is around - 4 volts, the grid may go to - 8 or - 12 volts, but current stopped flowing in the tube at - 4 volts, and the output waveform started clipping.  Biasing a tube closer to cut-off Distortion results in less power dissipation and is called cool biasing. 

As the voltage at the grid goes more positive the current through the tube increases until maximum current flows. Grid current Clipping occurs when we try to drive the grid beyond 0v.  Electrons being drawn from the cathode get attracted to the grid rather than the anode causing a forward grid current into the grid. This current causes a voltage drop across the resistance that is in series with the grid, making it hard to drive the grid beyond 0v.  It is the grid signal that is being clipped, while the tube amplifies what appears on its grid normally. The grid voltage may continue to swing more positive, no more current can flow and the output waveform will be clipped. Biasing a tube closer to Grid current Clipping results in more power dissipation and is called warm biasing.

To set the bias point of the grid to - 2 volts relative to the cathode. the Control grid is held at 0 volts via the grid leak resistor and 2 volts is applied at the cathode via the cathode resistor ( Cathode Biased).

An AC sine wave swings both positive and negative relative to the bias point, so if the signal is 3 volts, on the up-going signal the voltage at the grid will be 1 volt and on the down-going signal, the voltage at the grid will be at - 5 volts. 4 volts peak to peak is enough to swing a 12AX7 from cut-off Clipping to Grid current Clipping.