To add your logo to your account, click your initials in the bottom of the side toolbar then click Settings. From there click on Organizational Settings.
Where you see 'Logo' click the Change File button or Upload a file to upload your logo. Hit Save Information at the bottom of the page to save your selection.
Your logo will show up in the top navigation bar on the desktop as well as on the daily check-in screen for your clients within the app.
While you can use any type of logo you want, the ones that look best have a white background and are square.