New to prostate massagers, any advice?

I just got a prostate massager like a couple days agos and I don’t really know how to use them. Ive been listening to mindgasm lately but can’t understand how I can use what I learned from mindgasm and implement it with my massager. I have a couple questions to ask.

What muscle should I use when iserting the massager, the PC muscle or the base?

How do I stay relaxed and concentrate when doing prostate play?