To be able to request shifts through onDiem you must have an onDiem account.
Don't have one yet? Use this link to sign up and get started: Sign Up
Once you have created your onDiem account and completed the first 4 steps of onboarding, you are able to search for shifts using the "Find work" tab.
The image below is that of the "Employee Portal" tab within a professional's account. Each of the 4 steps needs to show a status of complete, to be able to see the "Apply" button on shifts you want to work. 