Open the rear cap window if of the canopy and also the tailgate of the truck.
Now you need to disconnect the electric connection to the canopy lights if applicable. In order to do that, get onto the truck bed. See how the electric connection was made. If it is a simple plug type connection as is the case with most pigtail electrical connections, you just need to unplug it. If the connection was made in any other way, just snip the wires using a pair of wire cutters.
In case you need to reinstall the canopy, it will be a good idea to mark the position on truck bed where the canopy was originally installed. Using a grease pencil or a permanent marker, mark the inside of the bed rail in several places where the canopy makes contact with the bed rail. This will save both effort and time when and if you decide to reinstall the canopy.
Now the canopy needs to be freed from the bed rail so that it can be removed. Depending upon the type of clamps that were used to hold the canopy to the bed rails, you need to choose the proper tool. Mostly, cap clamps serve this purpose. If this is the case, you need a ratchet and socket. Some people using regular C-clamps instead of cap clamps. C-clamps can be removed using a bolt driver.
Remove all four clamps holding the canopy in place.
You need to lift the canopy to remove it. Do not attempt to do it alone because there are high chances that the canopy will be a little too bulky for you to handle alone. Taking help from one other person would suffice and taking help from three other people would be great. Lift the canopy carefully and take it to a safe location.