@ceyanne At the moment there's no way to make a shared station "your own" on the Pandora app.
For now, you will have to sign into Pandora on your computer (http://www.pandora.com) and give any song in the station a Thumbs-up/down rating. Then indicate that you want to make the station your own (not shared). The next time you open the app on your device the Thumbs options should appear as normal. Hope this helps.
... View more