Watch a quick video showing you how to view multiple diaries, and scroll down for more information
I don't have this option...
You will need to be on the senior engineer role level or higher in order to see this. Please ask an owner/manager to set your role level appropriately if you do not have the necessary access.
You may also not see this if you have updated your app to the newest version, please delete the app, then re-install and you will see a prompt after logging in to turn on the multiple diary feature.