It's actually quite an easy puzzle, I have just finished it.
Start with the most identifiable parts of the image - the eyes. You should find them soon enough along with other facial features, then hair which are also easy to identify and orient. Work outwards to the rims, until you reach the white border, preferably in a corner part (I hit the lower right corner first).
Once you have that, you can shift the whole picture to fit into the frame, and if it fits, the correctly placed pieces will sort of "snap" into their precise positions, making further solving even easier. Continue to fill the missing rim parts until you have the whole picture, the end should be easy enough.
Try it a few more times, if you don't succeed, I will send you the picture. The puzzle is really easy, you should be able to do it.