This may be a dumb question, but I have a Lufthansa reservation that was booked by my employer and I am trying to add my MileagePlus account to earn points, since it is StarAlliance. I have the booking reference and can view the reservation, change seats, buy an upgrade, etc., but there seems no way to add a frequent flyer program to the reservation. I have tried on both the website as well as the Lufthansa App. I don't even see a way to add my Lufthansa award program (Miles & More) to the reservation. What am I missing?

The flight is in 2 weeks. I am very close to Premier Gold status with United and this flight would put me over the line, so I don't want to screw this up...

Thanks!