First envision a flag on your frame. Maybe even draw light pencil marks so you see it better.
Then working in sections {I suggest starting with the blue area first} start gluing down your buttons on the frame, in rows. My big suggestion is just put lines of glue/buttons down and then come back later to fill in any blank spots with another layer of buttons on top. Don't worry about filling in each little space, in at first. The more layers of buttons you are put on, the fuller it will look down the road. Remember - it doesn't need to be completely covered either! You are not going to be able to fill in each spot/corner because of the shape/size of your buttons. A little space is ok :- )
Another big suggestion I have, is to work in stages so you don't get overwhelmed. I first did the blue section, walked away and then came back for the red and then the white. It's ok to be a slow crafter on this step!!!
And finally - remember to let your Button Flag Frame dry completely, in a flat undisturbed away, when it's completely covered & done. * Then place a beautiful picture inside and display proudly!!!