Which car do you have? IIRC only the Touring offers the memory seats.
Regardless, the instructions for "customized features" comes to you via the Owner's Manual, in the section >Gauges and Displays> Multi-Information Display, starting on page 90. The options include "position setup", which defaults to "On". Resetting that to "Off" will prevent the automatic seat positioning that happens when you unlock the doors with the key remote fob.
For those playing along at home, the primary key fob remotes are identified with a "1" or "2", and coincide with the seat and mirror position memory settings stored using the door switches. While active, each of the two drivers would have their own key, and the seat and mirrors would go to the programmed positions as you enter the car. In our use, K and I each use the same key ("1"), so the seat and mirrors always adjust to stored memory positions associated with that key when the fob is used to unlock. If she drove the car more than once in a great while, I'd reset the position memory option to "Off". She would get to use the door button to use the other ("2") stored position when she first gets in, and it would stay there until it was changed either manually or via the door button "1".
If you get a replacement fob, you get to associate the new one with the desired seat memory. If you add another key to the collection, it won't take one of the two main memory positions while another is still associated with it.