In Poser, select the BODY of the figure, and look at the Parameter Dial menu. (If it's not up, bring it up under Window -> Parameter Dials.)

See what morphs are there. The ones that are not equal to zero are the ones you want to add. There may be only one, if it's a custom morph. There may be many, if the person who made the character used the DAZ standard morphs.

If there are a lot, use the "queue" function in the Tailor. Add the FBMs to the queue first, and when you've got them all, add them to the dress all at once. (It will take awhile.)