Glucose test help... What to expect as a ftm?

So how exactly does the glucose test work? I have heard that there is a 1 hour, and a 3 hour if you don't pass.the 1st... But what does that mean? You drink the stuff and wait at the office an hour for results, and the same for the 3 hour? Or do you drink it, leave the office and come back? If you pass.the test once, do they have you do it again later in pregnancy? I feel so silly asking, but this is my first pregnancy and I don't know really what to expect. I have 4 weeks before my test so of course it will be around Halloween when I have access to all that candy! Hahaha Thanks in advance for any info you can give 😊💙