Answer:
Wilma will be in charge of lighting the candles; we will not be turning on the lights.
see how after the word candles it looks like something is missing? that's how I knew where to put the semicolon. It can be used as a sort of comma.
Usually you use a colon when you're listing something, or explaining something. you can look up some examples for each.
example: There are only two choices this time: fight or freeze.
