I just finished my first game. I couldn't figure it out.

You press the ` key. That key is located directly above the tab key, which is left of the number 1 key. I believe it's called a tilde.

Be sure you use the US-keyboard. If not the tilde is somewhere else.

Norwegian keyboards have it by doing
1. alt gr and \
2. press any letter or numer key.

Messy but working.