Please explain how osmosis works. When the tutorial showed it, i saw a square on the screen. 2 more times it has happened and i do not see anything to click on??

I had the same question.  Use the magnifying glass icon on the Osmosis Event panel.  That takes you to the city in question.  On that city's name label, on the right side, there should be a science beaker icon.  Click on the beaker and you will see what opportunity the event presents.  (Sometimes, especially late in the game, nothing at all.)