Assigning a specific IP address for PC through router

I really don't know how to word the subject but hope that the people in here can help to solve this problem.

I have a static IP address assigned to a modem. From that modem I have a wireless linksys router hardwired to a desktop PC. I need for the wireless to assign IP addressess that connect wirelessly BUT need that one specific IP address used by the computer.

There is a program used by the computer that requires that specific IP address for the desktop computer for authentication purposes. How do I configure the router so that the web server on the internet reads the desktop computer as having that IP address.

You don't.. you port forward so that the web server on the internet talking to a port on the router will get the traffic forwarded to the desktop computer. Otherwise, connect your desktop directly to the modem.

I really don't know how to word the subject but hope that the people in here can help to solve this problem.

I have a static IP address assigned to a modem. From that modem I have a wireless linksys router hardwired to a desktop PC. I need for the wireless to assign IP addressess that connect wirelessly BUT need that one specific IP address used by the computer.

There is a program used by the computer that requires that specific IP address for the desktop computer for authentication purposes. How do I configure the router so that the web server on the internet reads the desktop computer as having that IP address.