Stepless clamps are designed to tighten in an exact circle around the hosing, simply use a crimping tool or the middle cutter on your pliers to crimp (not squeeze) the stepless clamp closed.

Many home brewers use worm drive hose clamps that can be handy because they can be re-used however worm drive hose clamps simply don't work that well on beer line.  The worm drive tends to pinch the line on one side causing the hose to leak or de-rates the pressure holding capacity of your system.  These stepless clamps are significantly better because they form even compression around the whole diameter of the line.  This makes a much better and more reliable connection.  

Also once attached the stepless clamps form a neater connection with no screws/bolts hanging off to get caught on things so they do make a neater more sanitary connection too.

*Crimping tool sold seperately*