...
Now the communication state is P2. Just switch the controller to P4 (CP4).
Open the tree-view. Mark the bits at the digital outputs (master->slave) that shall be set.
Now hit the button "F7" and the engineering will set the outputs. Check the data at your IO-Device.
Now set some inputs at your slave device. This inputs can get viewed in your engineering.
To leave the "force" mode just press "Alt+F7".