Step 1: Open your Skype for Business.
Step 2: Click on the person name tab to whom you will share your desktop screen.
Step 3: Click on the screen icon, then select the present screen option.
Step 4: After selecting the present screen icon the present screen is now visible, to share the screen you have to click on the present.
Step 5: Their is one Pop up occur, click on OK.
Step 6: Now you are able to share your desktop screen on Skype for Business.