airport timecapsule

Kind of a vast question !

If you need to create a network, the trick is to plug it only to power, but not to the internet, even when asked to.

Go through the setup until it says it is complete, then connect the ethernet cable.

OR :

Setting up Time Capsule for the first time - Apple Support

Hope this helps

(set up using AirPort utility, of course, which an OS X built in feature)