Firstly, you need to take a screenshot which can be done several ways. Afterwards, bring the picture into another program where you can easily add shapes or comments, such as Microsoft PowerPoint. This can be done easily by dragging the picture into the program, or clicking the "Add Photo" picture on the toolbar at the top and opening the file.
How to Add Shapes
1. Click the "Shapes" button on the toolbar and select which shape you would like to use.
2. Drag the your cursor out while holding down the left button to determine the size of the shape. You can then drag it to where ever on the slide.
3. To change the color or border of the shape, right click the shape and select the "Format Shape..." button to see all the options.
How to Add Text in Shapes
1. Right click the shape and there should be an option that says "Edit Text" which will allow you to write in the shape itself.
2. To change the font or size, highlight the words and right click it then select the "Font..." button.
How to Cirlcle Objects
1. Refer back to "How to Add Shapes".
2. Again, go to the "Format Shape..." button where you can edit the options for the shape you've chosen.
3. Remove the color fill of the shape by selecting "No Fill" under the "Fill" tab.
4. Change the line color and thickness by selecting the color options under "Line" and the weight of the line under "Weights & Arrows" on the tabs above.
Finally, when you're finished with your markups, you can save the page as a picture by clicking the "File" button on the toolbar above and selecting the "Save as Picture..." button.