How to add more network interfaces apart from default openstack private and pubic network in a VM

I am new to using this kit and using the available default flags in openstack i was able to create a vm which has one public interface and one private network.

/pkb.py --cloud=OpenStack --machine_type=m1.medium --image ubuntu-14.04-cloud-image --benchmarks=iperf --openstack_public_network=proj-net --openstack_private_network=priv_net

I wanted to add one more interface in the virtual machine with a different network configuration

how to go about it?