I had to do this the other day.  The C:\ drive of a client's server was getting full and I was looking for items to move over to a different drive.   The WSUS content database was pretty large and this is how I moved it.

- Open the Command Prompt.
- Browse to C:\Program Files\Update Services\Tools.
- Type the following command:  wsusutil movecontent D:\wsuscontent C:\wsusmove.log Where D:\wsuscontent is the new location, and C:\wsusmove.log is a log file for the move.

Keep in mind the folder for the new location must already be created.

I got this info from an Experts-Exchange.com post...