So, the first thing you should do, is read the new player guide, by the community for the community, so you don't jump in completely blind. It includes the basics of the game and has a bunch of useful tips to prepare you for your first time playing. Only takes a few minutes.
https://www.team17.com/hell-let-loose-new-player-guide/
Then, as for which server to choose, a lot of people recommend joining a server with "New player friendly" in the name. From my experience, it can be chaos on those servers, so at times you'll have a hard time finding a squad to play with (if you don't have any friends to join). However, the experience is also more casual. You're more likely to "fit in" so to say and not get completely destroyed. If you don't mind dying a lot however and are rather looking for a server with a bigger emphasis on teamwork and squad cohesion, don't hesitate to join a more "serious" server.



Officer role (squad leader) after you had some time as a regular infantryman.




I got the goods to dent it