Link Aggregation for WAN?

Hello all. 

I have a single ISP that has brought in two fiber lines for me, both on the same subnet. Combined they should be 10Gbps, and are on my SPF+ ports on a Fortigate 100F firewall. 

I believe, if I understand correctly, that I shoulod use link aggregation to combine these into a single 802.3ad interface, and assign the SPF+ ports to it, then give them my static IP.

Am I on the right track?