On the Edit page for instrument pads, you set up the sound of the kits.
To open the Edit page, click the Edit button in the upper section of the plug-in panel.
To show the parameters for a particular drum instrument, click on it. Depending on the setting of the Mute Instrument Trigger on Editor button in the upper right corner of the Edit page, this also previews the instrument.
If a drum instrument is triggered, this is shown by the instrument turning dark.