Are you trying to ensure that the wireless printer always uses the same address on your local network? You would need to set this within your router. As all routers are different you need to consult the manual to see if it is possible. If not, you may be able to set the lease time to 'for ever' so that devices always use the same address.
If, on the other hand, you want the router to use a static address to access the Internet, you would need to negotiate that with your ISP. They usually charge extra for that.