Cannot edit mesh after rendering I'm really new to this. I could edit this file until I had rendered it and now I can't. Please can you help me.

I've also tried to register as a User this evening, but neither of the links in the two emails you have sent me have connected me back to the Sign up process.
Your question is not too clear.

If you cannot get back to the 3d view port,  press escape and it should take you back.

If you're renders are staying the same, uncheck sequencer shown below.


If none of these answered your question, please specify in more detail.