How to power on this weird circuit?

[Zestfully4]

I have a pre-assembled DIY project I am working on for the sake of practice, and I'm perplexed as to how to power it on. Below is the schematic.

Based on it, VCC is on pin 7 of U2 and GND is on pin 2. However, the U2 component is not a typical IC as it's a board…

I have a 4.5V power source but can't seem to find a way to connect it to this circuit. I tried different combinations of red-black to one of the pads of the board and had no results. I'm a beginner student, so please be wary of that. Attaching circuit pictures from different sides below.

 

[rjenkinsgb]

It appears to be the two pads marked + and - next to Q1.

To confirm that, see if there is a copper track (on the underside of the PCB) from the + pad to the non-banded end of D3 diode, just near the connections?

 

[Nigel Goodwin]

Socket J1 is clearly labelled as the power input, 4.5V-5V - polarity isn't marked, but is obvious with positive to pin 1 and negative to pin 2.