How do I change instrument in a part of a staff - Musescore version 3.6.2

I have made a vocal arrangement and the instruments are defined as vocal. However, in some part of the staff I want to playback to sound like a piano and then turn it back to vocal some bars later.

I have managed to do this before, so I know it is possible, but can't remember how.
Nice if anyone can tell me how this can be done.

Best regard Geir