Put atoctx.el somewhere that emacs can find it, or add its path to the
set of load paths in .emacs:
(add-to-list 'load-path "path/to/atoctx")
Then just load it with
or what is perhaps a bit more intelligent
(autoload 'convert-buffer-to-context "atoctx"
"Converts the whole buffer to ConTeXt syntax" t)
although you won't have immediate access to the individial functions in
A set of elisp macros to convert some LaTeX commands to their ConTeXt equivalents.