The Choose Props screen is used to pick from the list of Props, those appearing in the shot. Click on the desired Prop and then on the ‘<’ button to move the Prop from the "All Props" list to the "Props Used" list. You can also double-click on the Prop name or if you want to add all the Props use the "<<" button.

Removing Props works the same way, by double-clicking or using the ">" and ">>" buttons.

Click the "New Prop" button to add Props to the "All Props " list.