gerber to dfx

Well I have converted the design made from HFSS to DXF file and now I need to convert the DXF file to Gerber on Agilent ADS. I set the different colors on layout to distinguish the parts on DXF file but I would like to know more in detail as to what i need exactly on gerber file that is satisfy to send to PCB express to be fabricated.

First you need to import the DXF to layout and then export to Gerber.
Its try and iterative process in setting the various check boxes