I found this information ridicolously difficult to find, so I thought I would post it on my blog so hopefully you don't have to go through the stress that I just did.
To make a port on a nexus 5548 (A universal port) both Ethernet and Fibre channel, enter these commands:
switch(config)# slot 1
switch(config-slot)# port 32 type fc
Where slot is 1 when your trying to configure the main ports on the actual chassis itself, and slot is 2 when your using an expansion module. You can also specify a range of ports with port 21-32 for example.
Short and sweet but I hope it help's someone out there!