To pause your monitor, it can be done in two different spots. First, from the main page with the list of monitors. Click on the 3 dot icon next to the monitor and a pop-up will appear with a number of options including Pause Monitor.
Once inside a particular monitor, it can be done by selecting the 3 dot icon in the top right corner of the browser and selecting Pause monitor.
Please note: When viewing the list of monitors on the first page, to see paused monitors, you'll need to select View All towards the top of the screen.