Manual means you have to assign an IP to each computer, instead of the router doing it via DHCP.
Check your Network Connections
Control Panel (Classic View) > Network Connections
Right click your current connection, then select Properties
Under the General Tab of the properties, select Internet Protocol (TCP/IP), then click the Properties button.
You will then see your IP settings. If you want the router to dynamically assign an IP address to each PC via DHCP, the "Obtain IP address automatically" should be selected. Then click the Advanced Tab, to make sure DHCP is enabled.