You should definitely get in touch with LH by phone, they are able to send you a separate pdf file containing your R&F reservation, especially if it's already been charged to your credit card.

The "personal pick-up number" is probably an awkward translation from German, but it refers to the 9-digit reservation number which should be located next to your name in the "info" section of the R&F-specific pdf file (unless they've changed the layout in the past year, but either way, it should be there somewhere).

The long-distance ticket machines are huge and aplenty at FRA near the train station, plus they are marked in English as well as German, so you really shouldn't have any trouble finding them. If I recall correctly, there's also a DB ReiseZentrum at the station, with a few machines inside as well. But I'm confident you'll spot them easily as it is.

When you've found a machine, you need to select something in the line of "collect pre-booked tickets" (you can choose English as interface language on the screen, of course). Just punch in the said reservation number and the ticket will be printed. The entire process is really much simpler than you'd think, it's just that it's explained in a somewhat unclear way, with many interchangeable terms used.