Help: Spawn object from widget into specefic location ONLY & NOT anywhere, images below

Can someone please help me with this small request please?

Basiclly I have a widget that when clicked on it can drag out a Tower object to be placed anywhere on the map from your liking, What I want to do is to make it only a specific location the user needs to drag the tower and put it in specific location that he sees on the map (say a green shining mark on the ground) How can I do that ?

please provide pictures with the answer, thank you so much

below some pictures of my tower spawn BPs