You have probably already done this, but in case you are reading the manual on the website, here is how to install the free trial version:
Click on the 'Download' button and save the file Magimir.exe on your computer.
When you are ready, open the file, and the setup program will run. You will be prompted for the name of a folder to install the program. Take the default option if you like. It will also ask you if you want to install Magic Mirror as your current screensaver. (If you don't, you can select it later in the usual way.)
Start Menu items will be created for Settings and Preview options, as well as an Uninstall item. Settings is what to choose if you want to play with the program as a kaleidoscope, and it also allows you to control how it will work as a screensaver. (You can also get to these features in the same ways as for any other screensaver.)
If you purchase the full version, installation is the same except you will be sent a link to the full version setup file - download that instead. Also, when it first runs it will prompt you for your name and license code.
Simply select the 'Uninstall' start menu item to remove Magic Mirror from your system. Or you can do it via the 'Add/Remove Programs' applet in the Windows Control Panel.
Manual removal - you shouldn't ever need this, but for the record it's not hard to do. Just delete the folder in which you installed Magic Mirror, and also delete Magimir.scr from your Windows directory. [The program does not install or update any system libraries/DLLs, so there is no risk of interfering with the operation of other programs when you install or un-install it.]