the instructions should be something like this .

1. load figure - zero pose at frame 1
2. load cloth item - adjust ti fit figure at waist
3. go to frame 25 , apply final pose to figure , ignore cloth item.
4. cloth room - new simulation , clothify cloth item , specify constrained group at waist, collide with figure , run simulation

The result at frame 30 should be what you are after

You may get a better result by specifying the other collision options in the sim settings