Time Capsule
Can I just connect the AirPort Time Capsule directly to my IMac via USB and use it as a Time Capsule or do I have to connect it to my modem via an Ethernet cable?
iMac, OS X El Capitan (10.11.3)
Can I just connect the AirPort Time Capsule directly to my IMac via USB
No, the USB port on the Time Capsule is there only to add a hard drive for additional storage capacity.
The Time Capsule connects to your modem or modem/router using an Ethernet connection. Then, the iMac can connect to the Time Capsule using an Ethernet cable or via wireless.