Error Installing MODX Revolution

I'm a novice trying to install MODX onto Media Temple GS and I am receiving an error -

Your MODX_CORE_PATH is invalid

In order to install MODX Revolution, you must first locate your core directory that contains the files required to run MODX, including this setup application. The current value specified is not valid and setup cannot continue until this is resolved.

ERROR: Your MODX_CORE_PATH is invalid; please specify the correct path in the field above and click Submit.


Any thoughts or assistance are appreciated

Hello,

What version are you trying to install? Traditional or advanced? Also you have everything in the same directory, or are you trying to put the core folder outside of a web accessible path?