Hi Pat,
it's only a matter of opening the files when selecting: darks, flats & bias frames - top left hand column.
You then can see them & tick them.
This video might help:
https://www.youtube.com/watch?v=J96e9HRbi-A
It's hard to do Ha with a Bayer matrix camera - as you have.
You'll need to play around with the settings as below.
Remember only one pixel out of every 4 will detect Ha.
cheers
Allan