The technical bit:

1. Click on the download link (you will be given the option to save to your PC)
2. Click 'Save'
3. Browse to the location where you wish to save the installer then click 'Save'
4. Navigate to the location where you saved the file.
5. Double click on the installer.
6. Click the 'Install' button.
7. Once the install has completed you will be asked if you wish to go to the Display control panel
8. Click 'Yes' if you would like to browse your screensaver options or 'No' to complete the installation.
9. Should you which to change your screensaver settings at any time, you can find the options in Start > Control Panel > Display and then in the 'Screen Saver' tab

These are the system requirements for the screensavers

Windows 2000/XP/Vista
5MB free hard disk space
128MB RAM