To share your screen just hit the Share button, then in the new modal that appears, you can choose if you want to share your full screen or a single tab, once you choose just to hit the share button and your screen will appear!
Check out the helpdesk article below and let us know if you still need support!
How can I share my screen in Markee?
We are so sorry you are having an issue. Please don’t hesitate to contact us at firstname.lastname@example.org if your issues persist.