You can download Google Earth from http://earth.google.com/
You have to set the .bin file that you download to be executatable, and then run it, to install.
chmod a+x GoogleEarthLinux.bin ./GoogleEarthLinux.bin
By default it installs itself in /opt/google-earth/ . It offers to make a link from /usr/local/bin/googleearth to the right executable, I recommend allowing it to do this.
Once it is done, to run it you just type "googleearth" in an xterm (X must be running). You can make the appropriate desktop icon or menu item depending on what window manager you are using.
If the splash screen shows up for some amount of time, and then all of X (the entire graphical environment) crashes (if you have graphical login set up, it will give you a login screen again, otherwise you will go back to the console), some people have found this to be solved by downloading the libGL.so library. It should be put in the /opt/google-earth/ directory:
cd /opt/google-earth/ wget http://librarian.launchpad.net/7037027/libGL.so.1 -O libGL.so.1
Some places on the web also refer to downloading it from http://www.ground-impact.com/libGL.so.1.2 . Here are links to a few discussions of the issue:
Performance Issue with Google Earth:
if google earth is slow in slackware Linux, check whether DRI is enabled or not, if Direct Rendering is enabled then disable "Atmosphere" effect from View menu -> [x] Atmosphere for smoother functioning of the graphics in Google Earth window.