"Router on a stick" is the term your looking for (CCNA)
let say vlan1 is fr x.x.100.x subnet and vlan 2 x.x.200.x (your current network)
if you have a managed switches then you will be asking the managed switch providers to setup the vlans. vlans are configured at the switch. all you will need to do is identify that the new subnet (vlan1) is inside on your asa. i do not kno if your doing routing on your asa but if you do point the new subnet to the gateway and you should be all set.
i think that this will help you out.
http://www.experts-exchange.com/Hardware/Networking_Hardware/Switches/Q_24160932.html?sfQueryTermInfo=1+creat+vlan