I've had this frame forever, it actually came with a wedding picture, but the glass broke, and instead of buying new glass, I bought an entire new frame...
Then you need pegboard (I've also seen materials such as heating grate covers and smaller pegboard used, but I was talked into this one and I didn't have enough time to look around.)
Anyway, you can have the people at Lowes or The Home Depot cut it to size for you if you'd like, for free as long as you buy the pegboard from them, but I didn't have time for that... so my hubby cut it out for me using a box cutter.
It's kinda ugly at the moment, but no worries, nothing a little paint can't help. I painted mine white using basic white craft paint. I thought about painting a damask design on it with gray, but for now it is okay.
I got S-hooks from Lowes at the same time as I got the pegboard, it was 1.98 for 6 and I got two packs. Use pylers to wiggle and stretch them out to fit on the board, secure the board to the frame (I just used the frame clips it already had but you can use a staple gun). Hang it to the wall and TADA!
It's perfect... still think I might add the damask stencil... who knows. :)