Obviously you are not going to be able to hire a crowd for every practice performance you do, especially right now with what's going on in the world. However, I have experienced plenty of ways to prepare for this so let me share my tips:
1. Do a lot of pretend recitals
I don't know what the format of your performances and whether you have introduce yourself, the piece, talk about it, etc. but whatever you have to do, do it out loud and in front of people. Your best bet will be in front of your parents or teacher, but you can be creative and even livestream this kind of stuff to your friends. The idea is to make your practice feel as real as possible, so that the difference between a practice recital and real one is minimal. You can also dress up in your performance attire, this helps a lot to because you feel more important (I can't find the time stamp but in this interview Julian Casablancas mentioned how when he dressed up a certain way he played music in that particular fashion, specifically a wedding band)
2. Destress
Performances in front of big crowds is nerve-wracking for 99% of people naturally. However, don't overthink it. Sleep well, eat healthy, take deep breaths, relax your shoulders, maintain good posture - basically anything a chiropractor or doctor would tell you. If you are operating like you are when you are relaxed, that will help you approach the recital in a more collected fashion then if you are pulling 4-hour of sleep a night and binging on alcohol
3. Reprogram your mind
Reprogramming is kind of a cheesy technique, but it personally worked for me. Keep repeating a positive mantra in your head (for me it was "You're the boss" because I felt like I didn't have control, but it's just anything reaffirming and confidence-boosting) every single day many times a day. You'll be amazed at what you can fool yourself (a paradigm shift :) ) into believing
Those are just some techniques that worked in my experience. Good luck!