There are two adjustment on your fork: One of the Right hand side and one on the Left hand side as you are seated on the bike.
The adjustment on the Left hand side is a pre-load adjustment. Notice the plus and minus on the dial.
Preload is the amount of compression the spring has on it before it is engaged. Turning the dial toward the "plus" (clockwise) will increase the spring engagement and make for a more stiff feel of the fork. Conversely, adjusting the dial toward the "minus" (counter clockwise) will maximize the travel of the fork and make for a more plush ride.
The other adjustment on your fork is the "lock-out" feature. That adjustment knob is Blue or Black depending on the model:
Flex, Stride, Groove:
Turning the dial clockwise (right) will lock the fork and will not allow it to compress. This can be useful when climbing hills so that the energy used to climb will not be lost in the compression of the fork.