So on the right hand side there is the inspector for selected nodes properties, but if you look at the top of that panel there should be a tab for the selected nodes signals called Node, I guess it's called Nodos in your localization based on your screenshot.
From there you should be able to set up and connect a signal for button pressed state(button down) or button released(button up) state etc. See the docs here for further info.
Now for the particles I presume you want it to do the particle sim/playback just once on the button press, so make sure to enable the one shotproperty for the particles node(if I understood correct you already have done that though). And disable the emitting property.
Next, assuming you have set up and connected the signal from the button to the script where you intend to trigger the particles from(note that I'll assume it's the script on the button!) you should now be able to do something like:
func _on_Button_button_up() -> void: #this line should already exist thanks to setting the signal up via GUI
var p = get_node("../Particles2D")
p.set_emitting(true)
And that should do it.
