Create Functioning LAN

Our OS is Windows 2000 professional. Our router is Linksys.

Problem:
Currently we share information between our computers using the ISP email or floppy disks.

I have followed all instructions setting up our LAN. I have created a workgroup name I have identified all computer on the network.

None of the computers on the network are visiable to each other and we are unable to share printers or information using the LAN

How can I set up a functioning LAN using Windows 2000 and the Linksys router?