How to properly set a DHCP reservation?

Hey,

I have a couple of devices (e.g. a NAS, a printer...) that currently have their IP addresses assigned by DHCP. I would like to create static DHCP reservations for them but I'm not sure how to do the whole process correctly. If I'm not mistaken I can do the reservation in Services -> DHCP -> Leases where I can click the "Add a static mapping for this MAC address" button next to a desired device's entry. The docs say that I should choose an IP address outside of the DHCP range for the reservation. Is there anything else that needs to be done? And if I create DHCP reservations for my devices' MAC addresses via this method, how do they actually get the new IP addresses? Is it enough to just reboot them?

Thanks!