Log on, create or go to the appropriate folder (which should definitely be inside private!), and type clisp. (Variation: clisp myLispFile. This runs clisp on myLispFile and quits.)
If you really want to go there.
To load a file, (load "myFile.lisp") or maybe (load "myFile"). Note that when you load a program, LISP won't print any results, unless you tell it to with a call to PRINT (or some other function that prints). Ordinarily, you load a file of code, and then type in a function call to run the program.
When something goes wrong, clisp kicks you into the debugger. It will say Break 1 or Break 2 or something. Hit Ctrl-D to get back out (maybe more than once -- twice for Break 2, e.g.). Ctrl-D too many times kicks you out of LISP. You can just stay in the debugger -- it doesn't hurt anything.
While in the debugger, you can type the name of a variable you want to evaluate, or use up or down to go up the stack frame (roughly, the call stack).
To correctly indent a line in emacs, hit tab on it. To correctly indent a list, Meta-X indent-sexp.
To quit, type (quit).