There are a few parts that you need to be careful with, especially of you're fairly new to electronics.
- Make sure that when you're installing the IC socket and the ATmega you matches the notches with the notch outline on the PCB. If you don't, the proper pins won't connect to else where on the board and you're metronome will not work.
- The only component that is polarized here is the LED. Make sure that you put the shorter lead of the LED in the whole closest to the outside edge of the board matching the flat edge of the epoxy case to the flat marking on the PCB.
- It does not matter which directions your speakers leads are.
- When connecting the battery holder, be sure that he red lead goes in the hole marked V+ and the black lead goes in the hole marked ground.
- When inserting the ATmega, you may need to bend the pins so they are perpendicular to the IC's body. To do this safely, lay the ATmega on it's side on a flat surface and use your index fingers on the underside of the body and your thumbs on the top as seen in the photo. Then rock the chip forward to bend all the pins on that side evenly. Do this to both sides.