I'm not familiar with the toneport gx personally. Firstly read any instructions it comes with. Then i would suggest the "getting started" guide in Logic.
If you haven't already done so plug the interface in to your mac via firewire or usb.
Now, start Logic. Go to Preferences>Audio..
select your interface in the "device" drop down menu.
You should be good to go now.
Select an audio track in the arrange. Make sure it's I/O is selected (e.g. input 1) and it's output is 1-2.
Now, click the R button (record enable) on the track header or at the bottom of the channel strip. It should turn red.
Your track is now "record enabled". Click on the record button in the transport when you have connected a guitar or mic into your interface's input 1 and your should now be recording whatever audio signal is passing through your audio interface into Logic!