You can get the Basic Rules online for free, which are enough to get started. If you want to get deeper into D&D though you’ll have to buy the Player’s Handbook, and probably also Tasha’s Cauldron and Xanathar’s Guide.

Then you should figure out if you want to play online or in-person. It’s much easier to find people to play with online but they don’t have the “vibe” of in-person games.

To find a group, there are several Discord servers, including the official one; there’s also r/LFG, though I’m not sure if they’re participating in the blackout or not; and you can look on Roll20 for online games, though from what I’ve heard that’s not a good option. For in-person games I can’t really help you.

If you’re going to play online, you’ll have to pick a VTT- virtual table top. Roll20 is the most popular one, and is quite simple. Foundry is the best one, but costs money. I don’t know much about the rest.

I think that for a beginner, a “one-shot” is a good way to learn the game. Basically a one-shot is an adventure that you’re supposed to finish in one session, instead of a campaign that might take dozens of sessions over months. It lets you dip your toes in without too much commitment. I’m part of this discord server for one-shots that is pretty good.

Also, consider that D&D is far from the only TTRPG (Table Top RolePlaying Game) system out there. Pathfinder 2E is the main competitor to D&D, it’s a pretty similar D20 based system, but it’s rules are more comprehensive and it’s run by a much better company (D&D’s parent company has done a lot of shady shit, including charging 3rd party creators ridiculously high royalty fees, mistreating their staff, and sending Pinkerton mercenaries to threaten a Youtuber who leaked a new expansion.)

Oh and also all the rules for PF2 are available completely for free with no strings attatched on Archive of Nethys.