they usually have 2x NO contacts, so 1 & 2 are probably for one side, 3 & 4 for other side.
from my limited experience with shutters, there is a 4 core to the motor - earth, neutral, live (up) and live (down)
you take a live feed to switch, and split live feed to each side. (most likely 2 & 3). output from terminals for up/down go to relevant live on motor
if existing remote is staying, then the control for that will usually have an aux input. but as its normally the same button on switch for open/close, your keyswitch may only have 1 useful side. i.e my shutter has a keyswitch & remote. the keyswitch feeds the aux switch, so turn key to left, it signals unit, and either opens or closes (opposite of what its previously done). the right side of switch does nothing