Just set the speed to one that you feel comfortable with.
But suggestion, as evidently a first time FSD user, you are going to have to learn to trust the car. It will take some time and the car will have to earn your trust.
Start out on mostly straight light traffic roads. Then work yourself up from there. You'll need to learn that coming up to a traffic light, with or without cars, that the car is going to stop. If the light is red it will stop and it will take off. It will take time.
I've had a number of times lately that maybe a bicycle will be on the should of the road. The car slowed down. waited to see if the road was clear and then moved left, passed the bicycle and carried on. My wife had already disabled FSD, I tolkd her to trust it (I had seen it work previously) and she turned it back and indeed, it slowed for the bike, we were near a curve, so the car patiently waited until we were clear, then there was oncoming traffic and once it cleared, the car passed the bike.