I’ve been asking similar questions recently, and I’ve had some good advice. The absolute first thing you need to do is get comfortable building Blender. Instructions are here, and you can get help on this forum with problems. I’m happy to help where I can, but it looks like you’re on Windows, which I don’t have any experience with.
After that, here are some things I’ve found while trying to get my head around Blender from a dev point of view, in no particular order:
- There’s some good documentation here - https://wiki.blender.org/wiki/Source - although it seems to be split between that page and the old wiki archive, and I’m not sure if the old wiki stuff is out of date now.
- There’s some documentation in the
doc folder in the Blender source tree - again, not sure how up to date that is.
- I’ve found it useful to use an IDE, I find it helps me browse the source more easily, and being able to set break points and use the debugger helps a lot. I say this as someone who normally loves to use a good old fashioned text editor ;-).
- Blender’s codebase is BIG, so pick an area of Blender you know well to start with, and focus on that.
- I’ve found it quite helpful to read diffs from other developers; knowing what code in what files they changed to fix a bug/add a feature is really useful. You can search patches here - https://developer.blender.org/differential/ - or browse the repository history directly for commits.
I hope some of that’s helpful - this is the first large codebase I’ve tried to get to grips with, and it can be intimidating!