Wallpaper setting help

[weesy]

I've made a few collages on pic stitch and taken some photos on my phone that I would like to use as wallpaper on my phone but it always makes me just use a small piece of the photo instead of it in its entirety. How can I make it work so it lets me use the whole photo or whole collage, what setting do I have to change or what do I need to do ? Help!