Measure the length of the wing (actual wing) , then measure the length of the wing (on the plans), then measure the length of the tail on the plans.

Take the Actual Length of the wing and multiply by the measured tail length (on the plans) and divide by the Length of the wing on the plans. This will give you the length of what the tail should be.

Is there an elevator Joiner included with the kit?

What specifically do you have questions about? There are enough people here that can talk you through each step, looks like most of the hard work is done. It is a nice looking plane.