From the diagram you provided, the hypothesis for this experiment could be--plants grow taller when exposed to direct sunlight.
The independent variable is the sunlight and the dependent variable is the growth of the plant measured as its height in centimeters.
The experimental set-up testing the independent variable will be the plant grown by the open window exposed to sunlight. The experimental set -up that is used as the control is the plant by the window with the shade that is down and not exposed to direct sunlight.
Each experiment should have the same type of plant of the same size initially, with the same amount and type of soil, the same amount of water, the same size pot. The only variable that is different is the sunlight in the first experimental set-up. The control set-up which is not exposed to sunlight is needed as a comparison to see if the hypothesis is correct.
After a set amount of time-days, weeks, etc. and a collection of data including the height of each plant over time, one can assess whether or not the hypothesis is correct. If it is, the experiment should be repeated many times and the results shared with others. If it is incorrect, the hypothesis can be changed and a new experiment performed.
It is important to note that to have more valid results, more than two plants should be used in the experiment. A very large sample would provide more data to support or refute the hypothesis being tested.