I THINK I need link aggregation in my NIC('s) and switch

Got a very powerfull NAS Server running FreeNAS 8, and ive noticed that im not getting anywhere near the speeds i could be getting... im maxing out the 1GBps ethernet connection and i was sorta at a loss of what to do until i heard about "Link Aggregation". I was very happy when i found out that my switch aparently alredy suported it, and that the one NIC card i have in my NAS also suports it (Aparently). so now my question is, will it just automaticlly work if i get a second NIC of the same type or do i need some sort of cable to connect them, or do i need a whole new NIC, or do i need a new switch? I dont know how allot of networking hardware works, any help or words of advice you could give me would be nice :)