You would have to use the STATIC + CONDUIT commands if you know what ports you have to open up. If not follow my instructions in the thread :
Microsoft SQL and Ports for Outside Access to DMZ
Which can be applied in your case as well.
However there is the security aspect of this which I would like to warn you about. A good Firewall practice is to *NEVER* have any packets to pass directly from the outside to the inside. Your ICA server should be put into a DMZ, from where the ICA would contact the inside network to reach/run the applications which you have there
Best regards
Goran