Once you have an additional IP address, you need to assign it to a particular website on your server. Here’s how you do it:
1. Login to the Plesk Reseller Panel
2. Click on "Domains" in the menu you see to your left
3. Click on the domain name for which you’d like to setup the dedicated IP
4. Click on "Change Hosting Settings" in the options you see on top
5. Select the dedicated IP address you’ve purchased from the drop down list
6. Click on "OK"
Give it about an hour and your website will be mapped to your new dedicated IP. And that’s all there to it, really :).
