How to change order of items in wall/grid gallery

Hi! I’m trying to find out how to change the order of items in my wall/grid gallery. I have the PRESS section of my website in a wall/grid gallery and I want to change the order of the articles. (Right now the articles are in the order in which I added them, but I want to put the more important ones in the first).
How do I do this?
. Thanks for your help.