New user
Look through the Wanted:Players forum, there should be plenty of D&D games listed, they usually stipulate which edition rules they're using.
Where you're new to gaming, it might be advisable to start with a low-level game, so there aren't as many bits and pieces of your character to keep track of (5E may have made this advice less applicable, I don't know. 3E had all kinds of skills and proficiencies and level bonuses and...for someone new to gaming, I could see it being a daunting task to keep track of it all if you 'jumped in the deep end' and started with more advanced characters).
When you find a game that looks appealing, and you Request To Join (RTJ), be forthright with the DM about your lack of experience with gaming, 8n general, and with D&D. Most DMs will be fine with it, but it's to your advantage that they are pre-warned that you may need a little extra help keeping it all straight or understanding the game mechanics.
Keep in mind that some aspects of tabletop play get compromised in the play-by-post format, just to improve the overall flow of the game. Combat rounds that would be resolved in a few minutes in a tabletop setting may take days, depending on how many players are involved and how often they can post. So your DM may cut some corners, simplify combat, or 'handwave' things in play-by-post, just for the sake of expedience... when and if you get around to playing face-to-face, you shouldn't expect it to run the same way.