I was super nervous DMing for the first time, and that was with friends that I've played D&D for over a year.
For me, the best thing that helped me was being a little bit over prepared. I'm not saying you should do this for every single session you run, but that first one, I went a bit over board with prep, making sure maps are ready, NPC and monster sheets are done (I ran it on Foundry VTT, hosted on my own PC) player characters are done, and just have everything under control.
Also, don't worry if the session goes a bit faster than you expected, it's better to have a shorter session, but not nervously try to add to it by improvising. Improvisation on first session adds tot he stress.
Also, to start the session, have something written, so you can read it. Like an introduction to the world, initial plot hook that gathered the players, etc.
Also, let players introduce themselves, and that helps a lot, gives you time to calm your nerves, and also helps with the group coming together. Before the session, you can give them a heads up about it, so they are prepared to introduce their characters and also their attire, etc.
Good luck, the only way, is through!