Type the text with black color on transparent background.

Open the image.

Drag the image on the text layer. The layer palette will look like this. Select top layer.

Layer > Group with Previous (Ctrl+G)
The image will fit in the text.

File > Jump To > Image Ready 3.0
Duplicate the frame and select second frame.

Make sure that top layer in the layer palette is selected.
Move the image slightly towards left or right with move tool.
Set the timings for frames.
Set the no. of time you want to play the animation.
After completing the animation try to check the performance in the browser
File > Preview In > Click the browser you want

Save the file with File > Save Optimized or File > Save Optimized As