Open Facebook in your browser, and sign in to Words With Friends. It will take a while to load.
The Error screen will appear. Close it (it's touchy - if not done exactly, it will try to open a browser window to take you to Safari or whatever. Just try again.)
Here's the solution to moving letters - touch the letter you want, and while still holding the letter, touch another part of the screen. This will hold the screen in place while you drag the letter into place. When the letter is in place, release both the letter and the other part of the screen that you had touched. The letter will hover over the space you want - tap it to place it.
Repeat for other letters.
Occasionally the tile row will blank out - moving the tiles around sometimes helps. Otherwise, reload.
I find that raising the screen up so that there is white at the bottom helps, and use that white space to hold the screen.