If we read the ScriptCraft documentation, we can see that there are two different ways to do sounds, and one is really easy. You just need to know the name of the sound and give a location, for example:
Now you should be able to add sounds to any of the plugins you have previously made.
Here are some ideas:
entityChickenAmbient()sound to make your Chicken Transformation Wand cluck when you use it
blockIronTrapdoorOpen()sounds when you seal the room with iron bars in your Escape Room.
blockNoteHarpsound whenever the Lifesteal Sword regains health
The possibilities are endless. Sometimes you will need to create a new function to fire on a different event, like the Projectile Launch event, if you wanted to make your explode bow sound like a launching firework when you shoot it.