1) Buy cross-over RJ45 cable.
2) Plug cable into RJ45 port on each computer
3) Configure IP address on each PC - e.g. 192.168.0.1, 192.168.0.2, subnet mask 255.255.255.0 (network properties)
4) Ensure that Windows file sharing is enabled in Network Properties (file & printer sharing)
5) Share folder on target PC
6) Set NTFS security permissions on folder (if applicable)
7) Browse or map drive to shared folder on target PC
8) if requested for a username & password, provide a valid username & password for the target machine e.g. computername\username
If all else fails, RTFM
Windows Help is pretty good - the section on networking and file sharing should contain everything you need.