You can use the Properties Editor to apply screens to objects.
After you select objects that you want to apply screening to, you must apply your choice of screen instance to the selection. You can use the DotShop Properties Editor to change a selected object's screening properties, depending on the options checked in the SIF file for a particular screen instance.

Use the Properties Editor to:

To erase any changes you just entered in the Properties Editor, before clicking Apply, click Revert.