Running install.php

If I do not have shell access on my host, do I simply open install.php in a browser at the site to install? The intallation docs are vague on this point. When I attempt installing by opening install.php in my browser while logged into my hosting site, I get some HTML of the install interface on my screen, but also some of the php code. Entering the weblog title and my email anyway results in a Not Found error, I think it’s looking for the WP files in the main hosting directory(?). Am I missing something obvious here, can someone be more explicit about the installation procedure? I’ve already checked with my webhosting, they say they’re compatible with WP. Thanks.