I have a couple of these Hope seat post quick release, but I realised I don't know how to tighten it. I am referring to the adjustment on the bolt (not the qr lever).
Just the same as with quick release levers for your wheels, these are essentially a nut on one side with a bolt through it, with the lever attached to the bolt on the other side.
You can damage the clamp itself or what it is clamping, such as your frame or the seat post, if you over tighten it.
To get the correct tension (from too loose), you should open the lever (red arrow) fully, and tighten the nut (blue arrow) a little and reclose the lever (red arrow). Do this until it is at the proper tension.
Alternatively, if it is too tight, you follow the same procedure as above, but loosen the nut a little instead of tightening it. An easy to remeber rule of thumb is you want the lever to just be tight enough when closed for the seat post to not move.
As a side note, some people, and me included, leave the seatclamp just a tiny bit too loose on purpose for mountain biking, BMX and street trials, just because if I fall, I would rather my seatpost swist on impact rather than maybe damaging either the seat, the post or the frame.