How do i add am additional 8962 form for multiple 1095a's

You only get one Form 8962, the 1095-A forms would be summarized on it. You will see an option to enter another Form 1095-A after you enter the previous one.

Is there a button at the bottom of the form?

When you edit your Form 1095-A entry, on the screen that says Here's what we have for your 1095-As, there is an option that says Add another:

Ok, thank you!!