YOU have to add both names X AND Y
But  add just  1 lady profile description on Y or X

and add both adds
on the profile review

Not sure if  I was clear
you can take look on my doubles review
to have an idea
Hope helps
CARLA

So I had my first double today, with a provider I see from time to time who brought along a friend. They both have separate ads on backpage, and a doubles ad. Any advice suggestions?

The lady you provide the info about in the review grading process s/b the lady you already know.  Also, a doubles review brings a 10 rating into play, if other the criteria are present (DFK, BBBJ) that allow you to grade above 7.   The fact that your friend brought along another provider with her gives you that extra bonus criteria to grade at 10.  If this was your first double, and your expectations (which should have been stratospheric) were met or exceeded, it was indeed a once in a lifetime experience, no?  At least until your next...  

Also, remember that the second lady will likely have a very positive impression of you now, and be delighted if you decide to contact her and meet solo at some point...

....we have had alot of fun together and I am glad.  Many, many thanks to you....