I played around with this stuff when I first got the phone, but I'm running a Google Edition ROM at the moment, so I don't have access to those features.
Open the Gallery app.
Browse to the photo that you want to edit.
Tap the photo, and then tap Edit > Retouch > Sequence Shot. You'll see frames that you can combine in one photo.
Select the frames that you want to include in the sequence shot.
Tap Done.
Tap > Save. The edited photo is saved as a copy. The original photo remains unedited.