To add another stage to a venue record click on the Add New Stage button to the top right of the screen when in the Venue Stage section of Master Tour Venue.
Upon clicking this button a pop up window will appear on the screen for a user to enter any basic required information about the stage to be able to add it. A user can also set this new stage to be their main stage if they wish to do so by checking the box beneath the Stage Type field. When all required information has been entered click the Add Stage button at the bottom right to save the stage to the venue.
After that has been completed the new stage can be found listed in the Active Stages section, and underneath the Main Stage record.