Can I use Time Capsule as shared disk
Just to add to the first answer, yes you can use it as a shared drive (I do) It will also work with PC's not just Macs, so for example if someone came round your house with a Dell laptop you could give them access to it. 

This is a great way to share photos with friends, and also a good way to back up a PC as you will not be able to use Time Machine.

To answer the hardware issue, you will not need any additional hardware providing your computers have WiFi cards if not then you will need a WiFi adapter, or you could connect via ETHERNET.