If the jeans are modeled for La Femme and you are using LF2 as your base figure, you need to apply the La Femme body shape in frame 1 of the simulation.  Move the pointer on the Animation Controls to frame 5 and remove the LF morph on LF2 (set the tool shape to zero).  Click the Calculate Simulation button and allow it run for as many frames as you create.  The jeans should fit the figure in its A-pose.  In the last frame, pose LF2.  Nevermind, if the jeans don't fit anymore, you are going to recalculate the simulation.  Run Calculate Simulation again.

It occurred to me you want to apply another morph, so set the Animation Control pointer to frame 8 and apply the new morph. Again, you should recalculate the simulation.