signature in private sign key

I don't want to mess it up, so I'd better ask. I read the instructions for setting up the private sign key, but I don't understand the box below which says "Signature". I may be dense to ask, but what is this? Does it want me to link to a photo of my signature or what? Please don't think this too niave a question. Setting up the signature seems to be a very important process. I'm ready to publish the first app and this seems to be the only thing left I need to do before submitting the APK to Google Play.

Can anyone please tell me what this field wants?

Thank you
Anton Brzezinski