I still feel like I struggle with it quite a bit haha. but my advice is pretty general stuff... looking at and drawing studies of real bodies whenever you can. I don't think I'm great at figure drawing but it definitely makes a difference doing some sketches from photo ref before I draw a nude. I mentioned in a previous ask (https://retrospring.net/@carnagehallway/a/112538312145688498) places I like to look for IRL reference specifically for nsfw, but for some general body studies heres some more links: https://line-of-action.com/ https://anatomylearning.com/ https://www.anatomystandard.com/
- get copies of the morpho anatomy books, or the 'anatomy for sculptors' book (e-hentai.org has a good selection if you search 'morpho' or 'anatomy artbook')
- find artists who draw bodies in a way you like & try understanding their shorthand for parts of the body & why they make the decisions with their drawings that they do. but also a lot of artists (myself included...) cheese it with anatomy lol so make sure you're also learning what the body really looks like IRL, not just studying other people's drawings.