Turn out my particular model of the Maytag dryer was either manufactured by Whirlpool or used the same parts. I look up instruction on different sites and the belt diagram all showed that you should do the flat side againts the tumbler. Well, it was not the case for this model. I almost gave up after 4 hours of struggling to get the belt on the tension wheel and wheel at the end of the motor, I remembered that when I ordered the belt, it said the part was manufactured by Whirlpool. So I looked up directions for changing a Whirlpool dryer belt and sure enough, the diagram looked more similar to my Maytag dryer.
Anyway, for this model, the ribbed side of the belt needs to be facing the tumbler. The tracked marked by the old belt confirmed this. Then you just zigzag the belt onto the 2 wheels. See attachment.
Below is a link to a youtube video that helped me.
When done correctly, this was a 15 minute job. So hopefully, if you have the same model as mine, you won't be struggling so much with it as I did.
YouTube - 27" Dryer Belt Replacement (part #661570)