I don't know about your system, but my pidp-8 software is located in /opt/pidp8i .
So to run the application, the path would be /opt/pidp8i/bin/pidp8i.
The pidp8 should always autoboot given the switch settings . For example if set to 0, then will boot into os-8.
Now if you just want to run the pidp8i program when you pull up a cli (whether using ssh to get into system, or via the gui), then there is a file called .bashrc in the home/<your username> folder.
$ nano .bashrc
goto the bottom of the file and add the line: /opt/pidp8i/bin/pidp8i
save it by ^X
then Y <enter>
exit from cli, and restart it. You should be in the pidp8. to exit that is ^A d and back to prompt.
Hope that helps