From swinging facing the platform, rise into a position (for example Planche) at the frontend (since you are facing the other way, this is the same as doing a backend trick for a catch). As you come back to the platform let go at the peak and grab the platform support with both hands, landing with your feet on the platform. This trick is simplest to perform in a Planche position, but can equally be attempted in a Split or Birds Nest.
You can find out more about this trick in my books:
Thanks to Envol, Adam (Mid-Air Circus Arts) and Renato (Mestre Trapeze Academy) for providing videos for this page.