I was looking at this article How to make a Qt Widget grow with the window size? but when i got to the answer I got stuck on "activating" the central widget. I notice an icon with a red circle so I guess that means its disabled. I've been searching the net to try to figure out how to "activate" it but I am not having any luck.
Can someone please help me out?
Have a look at the layout system. That icon does not mean your QWidget is disabled, that just mean you do not apply a layout on it. Try to press like Ctrl+1 in order to apply a basic layout. If nothing has changed, you might need to put a QWidget inside the central widget first and then apply the layout.