Use a 10mm wrench or 5mm allen key to loosen the bolt indicated below.
Remove the shifting pin from inside the axle and set it aside. It needs to be clean and greased upon installation, so set aside in a clean place.
Loosen both axle nuts.
Turn the 10mm nut counterclockwise to lower belt tension. You will likely want to turn it at least 10 times to reduce the tension enough to lift the belt off the chainring.
Once the tension is lowered enough, you can lift the belt from the chainring.
The chainring is mounted via 5 chainring bolts to the spider assembly. Note how it is on the inboard side of the spider and has the tooth count marking facing outboard. Remove all 5 chainring bolts using a 5mm allen wrench. I like to work the hardware while it is in the bottom of its rotation so that I can access the bolts from both sides.
You can now rotate the chainring slightly and slide it off the cranks and over the pedals.
Installation is the same as removal but in reverse.
Slip new chainring over pedals and cranks and into position at the spider. The chainring is a-symmetrical so it's important that it is oriented so that the side that reads 63t is outboard (only one side has the tooth count marking). It also needs to be mounted inboard of the spider. See the image below:
Install chainring bolts. It is recommended to grease these lightly to reduce the chance of creaking and corrosion in the long run.
Put the belt onto the chainring and ensure that it is sitting on the rear cog properly.
Increase belt tension to proper specs. Tensioning a Gates Carbon belt.
Align the wheel straight and tighten down the two axle nuts.