Hi Jessydc22, As long as you’ve a registered Ribbet user, you should be able to re-open your collage from the Library Tab > History. You can then click the Undo button up the top right of the screen until you are back in Collage mode.
To get it to fit 8×10.25″ you need to then adjust the Proportions Slider down the bottom left of the collage options. Watch the image dimensions whilst using the slider. These are displayed at the bottom right of the screen in the zoom box. You need as close as possible to 799×1024. You might not be able to get this exactly, but within a couple of pixels will be fine.
Let us know if anything’s unclear or you need further assistance.