As with a physical phone extension, you can set your self to away or Do Not Disturb. Note that as with a physical phone, DND will stop your CloudPBX desktop app from receiving calls. Pending the call flow you have in place on your system, this may mean calls skip a stage of the call flow.
You can check the status of your extension at the top of the app. The icon should be green and the present status available to receive calls.
To set your extension to DND, click on the drop down arrow next to your status. A menu of options will appear. Select Do Not Disturb.
To set to available again, follow the same steps, but select Available.