How can I configure SQL Server 2012 to use multiple NICs?
As long as the OS is configured for NIC teaming SQL server will use the team.  SQL Server doesn't talk directly to the network cards, all the communications goes through the TCP/IP stack which is a part of the OS.  However the OS is configured to use the NICs will be how SQL Server uses the NICs.

To do what you describe will require doing NIC bonding (aka. NIC teaming).