You need to turn on sharing in your laptop to make your files available to connected computers.
1. Right-click the disk that is to be shared, and select Properties from the contextual menu.
2. Click the Sharing tab.
3. Click "Shared as", and name the selected disk.
You need an ethernet crossover cable, or regular ethernet cable and a network hub to connect the two computers.
Use the 'go' > 'connect to server' menu in the finder of the iMac and hopefully the laptop will be in the list.