The Xfig user manual is available here.
Xfig/Transfig software is available here.
I started this site back in 1999 after having difficulty with downloading the software reliably from LBL and other sites. Xfig was the only software at the time that could handle my homebrew computer schematics. I hosted the software for the author at the time, and put up articles on Xfig. Eventually I put the Xfig software up on my Mountain Climbing Journal project on Sourceforge, but the maintenance of the software moved on from Brian and I transferred the Sourceforge MCJ site over to the new maintainer. This site remains. Xfig is still part of L1G3R, so if you are struggling to compile the libraries, particularly Xaw3d, step 443 and 445 might be useful. This has always been a troublesome bit of Xfig. Hats off to the current maintainer of Xfig as well as Brian.
Here are my collected articles with Xfig diagrams in them that I've created over the years:
2019-07-30: XFig Diagramming Tool