It would probably be good for you, as a prospective participant to have a few (body weight) basics down—squats, burpees, jumping jacks, at least a machine—before joining to get your money’s worth. But a good community gym with good instructors will have some type of introductory classes (usually 2-4) before joining the actual classes. For most gyms, you won’t slow anyone down, and you can “scale” (i.e., adjust the technique or reps to make the WOD match your skill level) nearly every workout.

For reference, I came in male, 6’3”, 175 lbs, decently fit, lean, lacking cardio stamina, average strength, and it took me 5 weeks of 4x/week participation to feel in a rhythm at my gym.