To use Google earth pro for free, first you need to sign up for a license and make sure that your system meets the minimum system requirements needed to run the program.
Windows based computers should be running XP or higher, and have at least 500MB of free storage and 512MB of RAM. Macs based devices have to run OS 10.6 or higher, along with the same storage and memory requirements. After that, you can download Google Earth Pro at your machine.