The first thing to do is to make sure that autoconf is available in your $PATH. You can do this by typing `echo $PATH' into your shell and making sure that you get the directory where you installed autoconf listed. If it's not there, you'll need to modify your $PATH before you continue.
More importantly, unless you're on a PS or dedicated server, you're probably not going to have any luck running LightSpeed. The LightSpeed web server is a full replacement for Apache which means that in order to run it, you'd need to have it running as a permanent daemonized process and listening on a port; both of which are not allowed under a shared hosting setup. What's more, even if you do have a PS, I think those have Apache running by default, so you'd either need to find some way to deactivate Apache (not sure if that's possible) or run LightSpeed on a non-standard port (which your users might not like). It's up to you how to press forward, of course, but you might want to give a bit more thought to the overall feasibility of what you're trying to do.