If you've been included for access to On-demand pay then you'll be able to see the earnings you can withdraw on the home page of the Onsi app.
If you don't see your earnings through the Onsi app then it's likely that you haven't been included for access. Your access is determined by the company that you work for so if you're interested in having this option please reach out to them directly.
Please note that some platforms will choose to make some but not all of your earnings available to withdraw through Onsi, so the amount you see in the Onsi app may not be your full earnings.
If you think that you have the incorrect amount available to withdraw then please reach out to the company you work with.