HOW DO YOU MAKE A LOOPBACK PORT ON A CISCO ROUTER?

The syntax that Funky gave you will work fine, you don’t even need to “no shut” a Loopback interface, they just come up. As to what kind of interface it is – this is a logical interface that never (typically) goes down. Loopback interfaces are very critical to network design, since they can never go down, and they never change IP’s, they are perfect candidates to consistently source packets from. The typical old-school example is when you are sending SNMP informatio. By default, you always source from the interface closest to the destination (the exiting interface on the router towards the final destination of the packet). If you have two WAN circuits however, or many WAN circuits, you might want a more consistent source address (you may for example want to lock down you Network Management to only except traps from specific hosts). This can be done by sourcing from a loopback. Same is true for router-id in a routing protocol, etc.
The are tremendously useful resource. Hope this helps to some degree!

try.
conf t
interface loopback 1
ip address 192.168.0.1 255.255.255.0
no shutdown
Then do a show int loopback 1
to see its status
or a show ip int brief
to see ip info etc.
Good luck