New StackAndTile user can't get it to work

I would like to try StackAndTile but I am not able to get it to work. In the beginning, it want me to resize the tables as big as I want them and then press F7. F7 for me is "airplane mode", so nothing happends in the width and height area and my internet shuts down. I got a Lenovo. 
Any idea what I should do?
Likely on your laptop, to press F7, you will need to press Fn+F7. If that doens't work, see this page for other alternatives:

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