Well, next step is to take a printout of the filled in application form on an A4 size paper. Affix the photograph, put your signature and left thumb impression in the space provided. I think even parent's signature is required. so get that done. Then you should get your Principal's seal and signature (the school or college where you did your 2nd PU or 12th Standard) on the space provided in the printed form. During counselling you will be required to submit this for document verification along with the copy of the Challan (KEA copy).  You dont need to send these to the KEA office for now.

My suggestion is to get this done so one aspect is taken care of in terms of the application form.

For which exam is this? You havent mentioned that so it will be tough for us to suggest the next step. Let us know that and then we shall get back with the next step.