If you use one servo per elevator half, you can use a "Y" connector to have them operate off of one channel in the transmitter, you can use two channels and use a mixer, or use the built-in Ailevator function. With the Ailevator function, you match centering with the linkage first and subtrim last. You want to use as little subtrim as possible. You set the endpoints of one side with the Elevator AFR and the other side with the percentage of Ailevator travel.

If you use a lot of subtrim, it moves the center point but not the endpoints. You want to make the linkages such that you are as close as possible first, and then use as little subtrim as you can.

The most common way to set things up is to use the Ailevator tail type. Just ignore the names. They just tell you which channel is activating which half. Just put one servo on the Elevator channel, and the other servo on the Elevator2 channel.