Open your WHM by typing http://you.cpanel.whm.host:2086/
Log in as server administrator.
Click "Install cPAddons" in "cPanel" section. You'll see "cPAddon Scripts Installer/Updater", which allows you to add/delete cPAddons.
Scroll down to "Add/Remove Vendors" section and type the following URL in "Vendor's information URL" textbox: http://www.afterlogic.com/cpanel/cpaddons/
Click "Update Vendors" button. After that, you'll see "AfterLogic" in the list of available Vendors and WebMailPro PHP in the list of available cPAddons.
Check WebMailPro PHP and click "Update Addon Config" button. Once the installation procedure is done, WebMailPro PHP will appear in the list of installed addons.
Now, domain administrators of your server will be able to install WebMailPro PHP from cPanel for their domains.
Open your cPanel by typing http://you.cpanel.whm.host:2082/
Log in as domain administrator.
Click on "Site Software" in "Software/Services" section. You'll see the list of cPAddons available for installing on your domain. In Email Section, "WebMailPro PHP" should be available for installation if the server administrator has installed it for you.
Click on WebMailProPHP cPAddon and you'll get to the installation screen.
Specify installation URL - URL under which you want to get WebMail Pro PHP accessible on your domain, and click "Install".
After installation procedure you'll get congratulations screen and full URL for accessing your instance of WebMail Pro PHP.
Next, you need to enter WebMail Pro PHP License key. Visit Admin Panel's URL of WebMail by adding /adminpanel to the URL provided on the previous screen. For example, if WebMail Pro PHP is installed into http://www.mydomain.com/webmailpro, Admin Panel will be available at the following URL: http://www.mydomain.com/webmailpro/adminpanel/
You'll see the following screen:
Specify your trial or permanent license key here and click Save.
Now, you can use Admin Panel to create domains, users, configure mail server and start using WebMail Pro PHP. Please note, however, that WebMail Pro PHP is not a mail server but a mail client, and users and domains you create in WebMail Pro PHP should correspond to users and domains already existing on your mail server.