Welcome!
Could we see a picture of the other side of the board?
There are different versions of the Tone Bender, and this one is a Mark II. The first transistor (Q1) doesn't require biasing. Q2 and Q3 do need biasing, you can use the two trim pots for that. Here's a process for that. You'll first be using the Q2 trim pot while measuring Q3 for a rough bias of both, then individually biasing Q2 and Q3 using their own trim pots.
1. Set BIAS2 trim pot and BIAS3 trim pot about in the middle of their range. Apply 9V power to the PCB.
2. Using a voltmeter set for DC volts, touch the black lead to ground (GND lug on the PCB is good) and the red lead to the Bias3 test point just under the BIAS3 trim pot.
3. You're going to use the BIAS2 trim pot to roughly bias both Q2 and Q3 at the same time. Measure Q3's collector at the Bias3 test point and adjust the BIAS2 trim pot until the Bias3 test point reads close to 8.5V DC on your meter.
4. Now fine-tune the bias on Q2 using the same BIAS2 trimmer. Move the red lead of your meter to the Bias2 test point. Slowly adjust the BIAS2 trim pot until the Q2 Bias2 test point reads about 0.15 VDC (150 mV) on your meter.
5. Now fine-tune the bias on Q3, this time using the BIAS3 trimmer. Check the Bias3 test point again. If it's not somewhere close to 8.5V DC, adjust the BIAS3 trim pot until it is.
6. Recheck the Bias2 test point, and if needed, adjust BIAS2 trim pot to bring it back to 0.15V (150 mV). This adjustment is more important than getting Q3 right at 8.5V.
7. Recheck Bias3 test point again for around 8.5V, adjust with BIAS3 trimmer if needed.
If this doesn't work, please post the voltage readings of the collector, base and emitter of Q1, Q2 and Q3 so we can see what's happening. Something like this:
Q1: C 8.5, B 0.05, E 0
Q2: C 0.15, B 0.07, E0
Q3: C 8.5, B 0.15, E 0.1