Once both computers are connected to the router, select all the folders that have to be shared between the two machines. Simply right click on each folder and select "Sharing and Security". Then check the "Share this folder" option and press OK.
You can share also the entire disk and not a single folder, it is your choice
Now you can open windows manager and type the IP address of the NIC card of the other machine.
PC1 has a NIC card with 192.168.1.10 IP
PC2 has a NIC card with 192.168.1.11 IP
to connect from the PC1 to the PC2, you have to type
Then you should see all the shared folders.
If there are no shared folders, you will see nothing of course
Alternatively, you can right click on the desktop and select New --> Shortcut. There browse the network places and locate the shared folders. In this way, you can go directly to the shared folder simply double clicking on the desktop shortcut