Assuming you are not real familiar with the M or H wheel arrangements (both the same setup, just size is different), the first thing we need to know is which way the wheels are turned. if they are dished in, step one is to turn them around so they are dished out. to do this you will need to support the tractor, and loosen the 2 bolts that clamp the wheels to the axle, both inside and out (2 each side). If they are already dished out, loosen the bolts and slide the wheels out. If the axles are rusty, you may need to clean with strips of emery cloth, wire wheel in a drill or grinder, etc. The can be loosened up if binding by driving in circles while carefully watching the wheel movement. You can even move them in and out this way, just be careful you do not run them off the end of the axle. A couple words of warning. You are dealing with a center dish weighing nearly 200 pounds, rim another 50 to 75, tire at a couple hundred, if it has weights, 150+ each. If it has fluid in it another 500 pounds per wheel. Ending up with a total between 400 and 950 pounds approximately per wheel. They can get you down and stomp on you once they are off the axle.
Here is me loosening the axle clamps at the age of 5. I was good looking even then
and a better picture of the clamps, not the bolts are turned down in this picture, and there is another set like them on the inside of the wheel. Do not be surprised if it takes a large cheater to loosen them. On one I hauled for Cub-bud I used a box end wrench with a 4 foot pipe slid over it and was beginning to wonder which was going to give first. Threads loosening, bolt (high strength) breaking, or wrench breaking.
I was in the process of installing more weights and getting new tires in that picture.