To install, add this directory to the load-path and add load the mode in the Emacs init file.
Example:
; ~/.emacs, ~/.emacs.el, or ~/.emacs.d/init.el
; ...
(add-to-list 'load-path "~/ql/misc/emacs")
(require 'ql-mode-base)
(require 'dbscheme-mode)
; ...