First time booking a resort

Hi! I got married back in May and we have had a lot of stuff going on and have been very behind on booking stuff for our honeymoon (we knew we weren't going to go right after the wedding). I know we are so last minute on this ):

Anyway, we have decided on Couples Swept Away. I'm booking through their website and have selected everything and am at the page right before hitting "complete booking"… but I'm confused as to how the flight selection part of this works.

I have selected the recommended flight but it has not asked me anything about seat selection or bag info, etc. (don't fly very often, so this is also new to me)

Am I supposed to book our flights on the airline website? I assumed the price that was reflected on the couples booking page was for the flights as well.

Any advice/help would be appreciated!