Usage of Photos for Portfolio Themes

I have an idea for a design i would like to create for the application. Now as background i would like to use a Photo of a snowy forrest i made with my drone. How can i prove that it is not a Stock Photo, but that i made it and got the Copyrights on it ?

I believe when you do the submission select advance and there is a place in the store that calls for copyright information. At least there is with The Watch and Android Apps.