Maskify (US$0.99) is a capable app for adding text, frames and masks to your photos. The app features 18 fonts in 20 colors, 18 frames in 20 colors, and elements for creating masks on your photos.
When you're done working you can save your creation to the camera roll, or share it via email, Facebook, Twitter or Instagram.
I gave the app a try and found it easy to use and it gave me very nice results. There are plenty of apps that include frame and fonts, but I thought the options presented by Maskify were unusually creative and attractive.
Instructions really aren't needed. You just select what you want to do, and apply the text or effects. The size and position of effects can be changed with finger swipes and pinches.