If the code base is huge, maybe just read some of the code your team has been writing (if you have a fixed team). Seeing how things are supposed to be called /

If the code base is huge, maybe just read some of the code your team has been writing (if you have a fixed team). Seeing how things are supposed to be called / used is also very important if you're collaborating with others on a project. Probably you'll find some internal libraries written by others useful. Maybe start with reading the parts related to what you expect to be doing? This of course comes after getting their consent.