tl;dr: I can create the info file, and it works, but install-info fails, and I think I found the issue. In addition, xmcsim doesn't seem to get installed, and there eis no examples dir in /usr/local/share/mcsim (but that may be correct).
Step 1: Yes, *info* is in /usr/share/info.
Step 2: I thought my mcsim/doc directory would be in /usr/local/share/, but that only contains mod and sim. I searched to see if it could be elsewhere, but it isn't:
/usr$ find . -name mcsim* -print
Is that a problem? I had thought I might have directory entries there for doc, examples, and perhaps even xmcsim.
I still have the directory in my home directory where I built it, and I did run makeinfo mcsim.texi yesterday in that doc directory. Since the argument to makeinfo appears to be the input file and my doc directory contains mcsim.texi, I figured that was correct. It created a mcsim.info file in that same directory. I think that worked, because I can run `info mcsim` in that directory and get what looks like a valid info session.
Step 3: I did not know or at least remember the install-info command. I should have tried the C-u C-h i trick, though; info works from there, too.
Running that command failed:
install-info: .: empty file
One more issue: While I haven't used xmcsim much in the past, I tried it, and it doesn't seem to work:
/usr$ find . -name xmcsim -print
bash: xmcsim: command not found
FYI, and thanks for your quick reply. I /think/ I did the install according to the instructions, but feel free to point out mistakes I may have made.