Installing skinz downloaded from the web or even creating your own is quite simple. Once you have installed ICQ Plus , go to the ICQ menu and click on the button, next to the online status.
It will give you the menu on the right which now has na extra selection . Clicking on the  will give you the console shown below, which is were you will install your downloaded skinz or create your own themes.

When you click on this button you will be presented with a window that will allow you to search your hard drive for the skinz file you wish to install. Though in most cases the file will be in a Zip format, there is no need to unzip the file yourself as ICQ plus does this for you automatically. It will also create a separate directory for your skinz and place all the needed files in this directory. Once the name of your new skinz appears in the ICQ Plus menu, hit the apply button to apply this skinz to all the options of ICQ and ICQ Plus.