Anywhere (and I mean anywhere) you tell someone they've booked a desk, you should include a map (or a link to a map) showing where that is.
In addition, you should label desks so people don't need to roam the floor wondering where desk 28 is (when they've just arrived in the office & so don't yet have their laptop powered up).
Texting them the booking & having a map an the entrance to every floor would also help