You can add plug-ins, replace a plug-in with a different one, and remove plug-ins from a channel strip.
Click the Instrument slot, then choose a plug-in from the pop-up menu that appears.
Click the Insert slot, then choose a plug-in from the hierarchical pop-up menu.
Click the MIDI plug-in slot, then choose a plug-in from the pop-up menu.
Click the Insert, Instrument, or MIDI plug-in slot, then choose a different plug-in from the pop-up menu.
Click the Insert, Instrument, or MIDI plug-in slot, then choose No Plug-in from the pop-up menu that appears.