open the catia file and click on fille / save as and select "stp" or "igs"
If these options are not displayed you need to upgrade your Catia licence.
We’ve added a translator that allows users to download a CAD file in STEP, IGES and STL formats, regardless of the format it was uploaded in. This makes it easy to share models with partners who don’t use the same CAD system you do. With just one click your supplier can download any of the neutral formats based on the original file you uploaded.
I outlined how to use the converter on our FAQ http://blog.grabcad.com/faq/use-file-converter/.
Have a great day!