What would be the appropriate adhesive to use?

[clover-grove]

I have a back room / mud room type of set up. The flooring is structaflor yellow tongue. I had planned to lay Hardie ceramic tile underlay and tile over the top. The James Hardie website just says "appropriate adhesive". I'm a bit stuck. My understanding is that thinset would be appropriate, however, I'm still stuck on what thinset to use. I unfortunately haven't had any luck speaking to people in store.

I was also hoping to use screws rather than nails. Is this okay to do? There's only recommendations for nails in the installation guides.

Thanks in advance for any help