If you previously had X1 you have a licence for Guitar Rig LE, which should show up in your NI Service Centre.
Download the latest update from NI and install that, using the serial number and registration code from your previous installation (serial number from your cakewalk account, registration code from NI Service Centre). Although it's called an update, it is a full installation.
If you never had X1 then you don't have a licence for Guitar Rig LE.
Hope this helps.