Filesharing on wireless network

I want to transfer files between two computers I have on my wireless network. Both computers access the internet through the router.

Cable modem -> Router -> Computers

What do I have to do to transfer files? Do I just need to install the Microsoft File and Printer Sharing setup? If I do this, is there any security risk considering both computers are behind the router?

Thanks in advance,

YB

just right click a folder and hit enable file sharing, make sure you have wep enabled or have no neighbors though.