Go to the next place that offers Judo lessons, pretty simple. Idk how it is in America, but here there are Judo gyms available basically everywhere.
Usually you ask to participate just to try it out. You would come in normal sport clothes because you don't have a gi or other martial arts clothes yet. Then you join the class like everyone else. Usually this means some kind of warm-up together. This might be playing basketball, some other kind of game that involves running, running in circles or more focussed exercises. Then all go in a big circle and do stretches. You'll feel like an idiot because everyone knows what to do but you don't. But nobody judges you because everyone has been there. People will help you.
In the main class, all kinds of things are done and all kinds of skill levels are present. Quite often they do different things. You will be doing whatever is done with a bunch of other newbs, one on one instruction by a teacher or whatever.
I've been the new guy a couple of times in a couple of gyms and it was never a bad experience.