If you are the Admin of an organization, and want to customize the logo displayed in the web portal so that it reflects your organization's logo, you can do that from the Admin -> Settings page: https://app.rundna.com/admin/settings
This video gives instructions for how to properly size an existing logo using Canva.
(Note that we are demoing this using Canva, but you can use any software you want. If you are using Canva, you will need a paid plan to use the Transparent box (you can try it without that, and it may look ok depending on your logo colors)