Clothes are not just props they can also be found in the "figures" folder. If they are conforming clothes, you must add them to the scene. You do that by first clicking on the clothing item in the menu and then clicking on the double check icon at the bottom of the menu.

After doing this don't forget to conform the clothing to the model. You might also want to take a look at the Poser 4 manual it does a good job of explaining all this.

Un coup de dés jamais n'abolira le hazard
S Mallarmé