I believe the best way to approach the academy is when they are actually hiring. I'm this way your chances of getting hired is much more. Also you can get a chance to show case your talents which is usually not possible.
Make sure you have a passion for being a police officer. Have the right mentality before you start. Make sure you're in shape & are able to take orders well.
Start eating healthy and do some physical fitness. When you do that then you would be prepared for the academy. It is good to do this with a buddy of yours so you would have some moral support.
like most people said, start getting in the best shape you can and quit eating fatty foods. Also, go in knowing that most of the work is just paperwork. My brother's friend is a cop and actually told me most of the people on the force aren't very happy with their career. I think it's because of pay though.
Be physically, emotionally, and mentally prepared for the activities/training that you will be going through in the academy. Also, make sure it's really your passion to become a police officer.