With a Lisp implementation that can be started from the command-line, installation just requires a few lines in your .emacs:
(setq inferior-lisp-program "/opt/sbcl/bin/sbcl") ; your Lisp system
(add-to-list 'load-path "~/hacking/lisp/slime/") ; your SLIME directory
(require 'slime)
(slime-setup)
The snippet above also appears in the README file. You can copy&paste it from there, but remember to fill in the appropriate paths.
This is the minimal configuration with the fewest frills. If the basic setup is working, you can try additional modules (Loading Contribs).
We recommend not loading the ILISP package into Emacs if you intend to use SLIME. Doing so will add a lot of extra bindings to the keymap for Lisp source files that may be confusing and may not work correctly for a Lisp process started by SLIME.