Click on your profile icon in the top-left corner of the Webex application:

 

Go to Availability > Do Not Disturb

 

Set the amount of time that you wish to be on DND. Your name will now have a 
 icon next to it

 

 

NOTE: DND synchronizes across your Webex Smart Phone app and your desk phone (if you have one) so you will not receive any calls on any of those devices while DND is enabled.

Click on your profile icon in the top-left corner of the screen:

 

Select Availaibility > Clear Do Not Disturb