In this tutorial you will make something like this...
1) Make the canvas 234 x 60 pixels, and make the background color black.
2) Write out a word, (Animation for ex.) and choose the color of the background therefore black.
3) Space the letter apart, not too far though.
4) On the timeline where you can click the lock button, there is a square on the right. Click it.
5) Draw 9 squares about the size of the letters. Make the boarder transparent.
6) The squares are all on diffrent layers.
7) On the title frame, add about 30 frames.
8) Now for the first square make a key-frame on 30.
9) Repeat step 9 now using square 2, 3, 4, 5, 6, 7, 8, and 9.
10) Now on square 1, go to frame 30 and put the square on the letter.
11) Repeat step 10, using squares 2, 3, 4, 5, 6, 7, 8, and 9 that you assigned to a letter.
12) Highlight everything execpt the title layer and right-click. Click create motion tween.
13) Now watch your movie if if it looks like the example below, then you did it right.
(The Line was extra 
)