Right-click on the bit in ladder and in the context menu you'll find Force On, Force Off, and Remove Force. You can also do it from a Data File window, but I don't remember if the steps are exactly the same. Also, forces can be "installed" (memory of which values are forced and to what), but also have to be "enabled" to take effect. There are pull downs to enable/disable/clear/etc, typically at the left end of the Online menu.
Finally, data file views can be set to an on/off display of forces, similar to a usage display.