Now go to your Yahoo! Messenger and open it if it isnt already open.
Click on the menu item "Edit".
Then click on Preferences.
If you're not on the "Appearance" tab, click on it.
Now you'll see a dialog that looks like this.
See the place circled in red in this picture?
In the area that says current Theme, scroll through them till you find the name of your new skin. Then click apply and okay. You should now have your new skin on
That's where you pick your new theme.
The name "frogland" will be in my dropdown list because that's what I named my theme!
Now, you're done!