What computer operating system is your Premiere Elements 12/12.1 on? Are you working from your own home computer or from a school or company network?
For a home computer Windows 7, 8, or 8.1 computer, you go to the Control Panel/Programs/Uninstall Program, and uninstall Adobe Premiere Elements 12 by finding it in the list of installed programs, and then right clicking it, followed by clicking on "Uninstall" pop up which appears.
Note: If you can still get into an opened project, you might want to Deactivate the program within the opened project, using Help Menu/Sign Out. After you sign out and close out of the project/program, then do the uninstall in the Control Panel area. Deactivation is not the same as Uninstall.
The following is the Adobe document on the matter.
Please let us know the outcome. Any questions or need clarification, please do not hesitate to ask.