Help designing for a LED Reader Board

I just got put in charge of our digital reader board at work and need to figure out the best way to design and save images that will look good and be readable on the sign. I've tried a few different ways of saving things but every time I load it onto the sign it gets distorted and choppy, which makes it hard to read. They have text that comes with the sign but they only give you 3-4 good fonts and not a lot of custom design. My biggest thing is getting a image with text onto it and it being clear and easy to read. Please Help!