Here are the steps to add a plugin which is downloaded as a Zip file in your system :
1. Open MyEclipse
IDE, from menu options click on Help > MyEclipse
2. Go to Software tab, click on [add site]
3. This will open a window, click on add from archived site, choose the downloaded .zip folder
4. Expand the ICEFaces plugin till the child node under Personal Sites, right click on the child node and click on [add to profile]
5. Click on [Apply 4 changes] button under Pending Changes section
6. Accept Software License
7. Follow the wizard and when prompted, choose to restart the IDE
8. To verify that the plugin is added, from menu options click on Help > About MyEclipse
Blue Edition > Installation Details > Plugins and verify the plugin.
Let me know how this works for you.