To remove your rear wheel shift your bike into the lowest gear and then loosen both axle nuts. Your wheel will now be loose. Slide it as far forward as possible to release the tension on your belt and remove the belt from the cog, then your rear wheel is free to slide out the back.
To adjust the belt tension on the Diverse 4.0 will start out the same way, shift into the lowest gear and then loosen both axle nuts. Now you're ready to set your belt tension. Pull your wheel back toward the rear of the bike until you can press down on the belt with your pinky and get about 1 inch of deflection. Once you have that make sure both side of your axle are even and tighten your axle nuts down.
Make sure you visit your local bike shop for a tune up and safety check to ensure you'll be safe riding your new bike.