You cannot "transfer" software from one computer to another.
- deactivate and uninstall it on the old computer
- download, install, and activate it on the new computer.
how do i deactivate it?
That depends on your operating system; most likely it is an option in your Help menu.
Adobe allows you to have the purchased activated serial number on no more than 2 of your computers. If all you have is Premiere Elements 12/12.1 on one Windows computer, then you should be able to use your installation files or installation disc and purchased serial number to install Premiere Elements 12 on your second computer.
If you purchased 12 as a download from Adobe, the installation files will be specific to your Windows computer.
Deactivation and uninstall are not the same thing. All you need to keep your "count" to 2 for allowable activated installs for the same serial number is just deactivate and then uninstall or not uninstall depending on your future plans. For Premiere Elements 12, deactivation is done in an opened project using Help Menu/Sign Out.
Please review and consider. If any questions or need clarification, please ask.