If you search for Mainframe in the knowledgebase (now accessible via a ? button at the left of the Portal) you will find an article titled 'How do I connect to my uncommon mainframe emulator?'
Your mainframe needs to be hllapi compliant (something all the enterprise terminal emulators are) - if it is not I would recommend your organisation looks to get an emulator that is hllapi compliant as it will pay for itself in speed of development and runtime when compared to using surface techniques against a non-compliant emulator.
