Pick up your bug and turn it on. It should briefly vibrate on both sides.

Place the but on a white piece of plain paper on a hard flat surface a wooden table top is ideal.

When the bug sees white in both its “eyes” it will start to run.

If your bug goes in a straight line, you are good to go. If (much more likely) it goes around in circles, you need to adjust the bristles of the brush and motor positions to correct.

You will never get it to go exactly in a straight line (if you do contact me and tell me how), but pretty straight is usually good enough.