After you go to the internet icon in the bottom right of festival plaza and connect to the internet. Select trade, link trade and a list will pop up. Any friends online should appear at the top of the list. Not a fan of the trading system in the gen 7 games it was much simpler in gen 6 in my opinion.
I don't know if that's how it will work for them to evolve. I own the old pokemon moon not the new one that you have, so I don't think it will work. Maybe it does for your new pokemon moon, but not with my.