When you check in on line, if they have not already upgraded you, there will be a box that you can click on that says request upgrade. Just click on that box and proceed with checking in. By doing it on-line 12 hours before the flgiht, you get ahead of the other E's on a H fare who check in at the airport.

My experience lately has been for some reason AC wants to torture us by not doing upgrades ahead of time, so you likely won't be confirmed until boarding time at the gate.