Trying to keep a basic answer (and assuming throughout that you have a recurve bow):
Hopefully you also have a plunger/button. (if not, this is pretty important to ensure your arrows fly true, so you should get one)
The rest attaches by a double-sided sticky pad onto your riser, making sure that the hole in it matches up with the hole in your riser that the button lives in. Ensure that the metal 'arm' is to the bottom, i.e. below the button, and that the magnet is nearest you (i.e. the arm points out and away towards the target as you hold the bow to shoot)
You then need to adjust the arm (in the case of this rest, I think by *gently* bending the metal) to acheive a couple of things:
1) with an arrow resting on the metal arm, the middle of the arrow shaft rests against the middle of the button tip.
2) with an arrow on the rest, and viewing from above, none of the arm protrudes out past the arrow shaft
You might possibly find that a *very* slight upward bend on last few mm of the arm helps an arrow to 'stay on' when you come to shoot.
If everything is set up correctly, as you shoot, the arm gets folded flat against the riser by the passage of the arrow, so it doesnt interfere with the vanes as they go past. Then after the arrow has left, the magnet pulls the arm back into place, ready for the next shot.
If you are at all unsure, any reputable shop or fellow club member should be able to help you get it positioned correctly.
Good luck.
