Now click on "collision", a window open, click on "Add / remove" a 2nd window open containing the elements of your scene, check the items that the clothing should take into account, here the character and the ground on which the fabric will come naturally spread. Click OK to close this window. In the first window still open and to accelerate the draping check only the elements of the characters who will not come in collision with clothing (here hand and head). Then select "OK" to close this window.