How to configure Cisco with 2 public ip address to different PC’s

Hi all
Can somebody can help me with a cisco router.

Here is the intended network setup
Setup two public IP address in the WAN:

ip address xxx.xxx.xxx.91 255.255.255.248
ip address xxx.xxx.xxx.92 255.255.255.248 secondary

I want to configure only one machine in the network to use the address ending with 91 and the rest of the network the address ending with 92. How do I link the 91 address to only one pc in the network and the rest to the address 92.

Thanks in Advance