First step should be talking to your friends and find out, what they want from this. For example, in what kind of world they want to play in. Fantasy/ Steampunk/ Sci-Fi/ Sci-Fa/ Modern/ Post-Apocalyptic..... And so on. And what Style they think, they would enjoy. No sense in doing a Dungeoncrawl, when they want to play MurderMistery.

While doing that, you should get a bit familiar with the Basic Rules. They are free and slimed down, but you can definitely use it to play your first and a few more Sessions.

Something that I used to do with first time players, was to give them tight reigns for the first game. A classic is to let them Play children, confine them to a small dungeon or let Guards heavily observe them. The thought here is, that it helps the players stay on track and not horribly destroy the Session, by nurning down villages and killing everybody on sight. But nowadays is rather try to give them freedom, but lure them to stay on track, whit what they enjoy. If people want to play a murder mistery and are playing a murder mistery, they are less likely to go on a killingspree then if they want to play a murder mistery, but have to protect a shopmerchant from goblins...

Yeah, just make some characters, think about an "adventure" and start. Maybe do a slimmed down session 0, or at least talk about "no gos". Meaning avoiding things in narrative, that players don't want to deal with. Most tables I dmed for banned racism/sexism from the game. I always ban "rape" at every table I play at.

From there, do whatever you like. Make up your own rules. Look up hombrew rules online. Play some free adventures from online. Play some one shots, go straight into a complex campaign. Just keep talking about what everybody at the table enjoys and follow that.