There's a ton of sources and resources out there, but as someone in the field of psych, I'd honestly recommend avoiding resources that do general psych that talk about BPD becuase they tend to push the narrative that people with PD's are permanently toxic and unable to be recovered (v stigmatizing)

Not sure what you're writing, so here's two different resources I used when I found out my bestie had bpd:

academic and treatment approaches:
www.borderlinepersonalitydisorder.org

For personal interpretations and experiences, there are reddit threads like this one:
www.reddit.com/r/AskReddit/...