how do i make a part react (like printing something) when clicked?

put a script inside of the click detector

and paste this inside of the script:

local Click = script.Parent -- this is for getting the click detector

Click.MouseClick:Connect(function() -- MouseClick is the event used for click
print("my parent has been clicked ;-;")
end)

did you even try to figure this out yourself before posting here? just typing"roblox clickdetetcors" brings up at least 500 results about how to use one. whatever heres your answer:

https://developer.roblox.com/en-us/api-reference/class/ClickDetector

its called .mouseClick