You'll probably need to add to the module's on-enter script. Something like this:
sub3(OBJECT_SELF);
oAreaObject = GetFirstObjectInArea(OBJECT_INVALID, 64);
while (GetIsObjectValid(oAreaObject)) {
if ((GetTag(oAreaObject) == "ptar_pazplayer")) {
AssignCommand(oAreaObject, ActionPlayAnimation(206, 1.0, 0.0));
}
if ((GetTag(oAreaObject) == "ptar_sitter")) {
AssignCommand(oAreaObject, ActionPlayAnimation(204, 1.0, 0.0));
}
if ((GetTag(oAreaObject) == "ptar_drinker")) {
AssignCommand(oAreaObject, ActionPlayAnimation(205, 1.0, 0.0));
}
oAreaObject = GetNextObjectInArea(OBJECT_INVALID, 64);
}
Check the on-enter scripts of other modules with sitting placeables to see what they do.
Edit: The 64 in the oAreaObject statement equates to OBJECT_TYPE_PLACEABLE. The 204/205/206 in the ActionPlayAnimation statements equate to ANIMATION_PLACEABLE_ANIMLOOP01/02/03, respectively. You'll want to check the model to see what animations it has to determine which you want to play.
Edit 2: Ah, that's right, the placeable sitters are actually just standard character models. The animations are on the S_Male02 supermodel. Looking at it in Max, ANIMLOOP01 is a static sitting pose, ANIMLOOP02 is sitting and drinking, ANIMLOOP03 is sitting playing pazaak.