@arkvet .... still looking but here is what I think happens now...
Back in the days of being able to select between Flight Service (at the time, LockMart) and DUATS, you had to tell FF which one you wanted to use and provide your login credentials for that system.
Now that the Graphical Briefing is what ForeFlight offers versus the old "teletype text" they had several years ago, that information only comes from Flight Service (now Leidos).
And to do the Graphical Briefing, you're using the information for the aircraft you created, which includes your tail# and type of aircraft, and the information you provide in the "Flights" area of FF, which is your route, ETD, name, phone, etc.
The FF documentation I have been able to find indicate that all that info is sent to Flight Service with the brewing request. So if Flight Service was asked by some official, "Did Bugmasher 987YZ get a briefing before their flight?" And you had your name and contact information associated with Bugmasher 987YZ when you did the brief request, then that's what would be found in their archives.
So to summarize, I'm not finding a separate distinct way to tell FF on your iPad or your FF account on their website to associate your FF account with your Leidos account. With Leidos being FF's only briefing data "vendor", and you inputting your aircraft details and personal details into Flights in order to request a briefing, all of the important and pertinent information is sent to Leidos for them to record.
Hopefully that maks sense..... If anyone finds a different way, please provide the correction.