Upgrading from Jomres Lite to Jomres Developer

From Jomres v4 manual

Upgrading from Lite to Developer is extremely easy. Once you've purchased your Developer Support and Download license you'll be able to either download jomres.zip, which can be uploaded via ftp to your /jomres folder, or you can upload the web installer (this is by far the better method, you can download it from the same page) to the root of your Joomla installation (that's the same folder that configuration.php is in) and run that.

Once that's been done you'll be given links to go to install_jomres.php which you must run to bring your site's tables up to date with the current version.

That's it, nothing else to it.

If that's a little oversimplified for you, then just follow the webinstall instructions for Jomres (Step 1 - Web Installer (recommended)), they're slightly more detailed.