If your profile is set up as a passenger you will only be able to book rides for yourself via the app.
Those with a booker or admin profile can book rides for themselves and other colleagues and guests via the web platform.
To book for others while using the app look for a person icon in the bottom right of the screen - this will take you to the mobile version of the web platform, with the same functionality as desktop. See User Roles for and Make a Booking section for more details.