These are the instructions i got with my purchase.
0. uninstall any other versions of Poweramp Full Version Unlocker if you have them
1. ensure your Internet connection is working on the device and you can open http://powerampapp.com
2. ensure your Google or Email account email@example.com is registered under Android settings => Accounts
3. ensure you have Poweramp build-550 or later from Poweramp website (http://powerampapp.com/ download-Poweramp). Play builds don't have non-Play purchase support
4. in Poweramp Settings use Already Purchased? => Website and type in Google/Email account firstname.lastname@example.org and Order ID xxxxxxx.
So you're saying all i have to do is reinstall the trial version and use number 4 from the instructions ?