To "force" someone to do something means to make them do it. You can use this word somewhat playfully:
They forced me to sit there and watch it.
Or you can use "force" to talk about something violent and frightening:
They forced everyone at gunpoint to hand over their money, phones, and other valuables.
You can also "force" yourself to do something.
I forced myself to sit there in front of the computer and keep working on it until it was done.
This means to use your willpower to make yourself do something that you don't really want to do.