If you want to create different audiences to use in your campaign without having to set up the entire campaign, you can do so using the Asset Manager which can be found under "Tools".
You'll be able to organise your saved audiences in folders and access them any time you want without having to create a new campaign.
To create a new saved audience, select the green "new asset" icon on the right of the screen.
Then name your audience, select your criteria and click proceed when finished and you will have a brand new saved audience to use when creating your next campaign.
You can now also create Custom Audiences in Asset Manager! For full instructions, check out our handy guide here.