Having sex for the first time

I'm 24 and have been in a long term relationship with my partner for a few years. I always told him I wanted to wait until we got married before having sex.

We ofcourse do other things but haven't had sex.

We are getting engaged and now I want to have sex but I'm very scared. I was wondering if there's any tips anyone could give me. I've never even put a tampon inside of myself so anything really could help. Thanksss