From the Storyboard:
Click the Branding tab.
Select your brand from the dropdown menu.
Confirm your selection and proceed.
From Edit Video using Text:
Select a brand from the dropdown menu to the right of the preview screen.
Your chosen brand and its components will be automatically applied to your project.
If you want your brand to be automatically applied to your projects, you can set a brand as default on the brands' page by clicking the star icon on the brand and the brand kit will be auto-applied to all new projects from that point forward.