Public IP address for SonicWALL

Am I correct in thinking that if I was to have a static IP for my router and a static IP for my SonicWALL, that I would need to ask the ISP to assign the static IP to the SonicWall before I can then configure it?  Or if I set the IP in the Interface that it would work?  I've never done anything with static IP's before.

Thanks.