First, Krakowiak welcome to our Community. I hope you'll enjoy being here and eventually make skins yourself.
That's an easy question to answer.
First, you have to uninstall the trial version. You can do that easily with CCleaner. It's free on the internet. http://www.piriform.com/ccleaner
After removing it, reboot.
Install "Impulse". You have to. This is Stardock's installation and update platform. It's free: get it here: http://www.impulsedriven.com/
After doing that, use your email and password to make your account. Make it your account here. Then, after logging on, go to "Explore" and type in the search box "Windowblinds" (or "Object Desktop" - a better deal), and it should appear. then click on it. (or double click) and a new indow should open and click on "Purchace".
When purchasing, use the email from your account here. If you have to use paypal, then you'll have to do an additional step later.
After purchasing and receiving the confirmation email, Windowblinds (or Object Desktop - whichever you decided on) should appear in the "My Software" tab as "Available for download".
Download, install (should happen by itself) and reboot. You're ready to go.
