Oliver Pay is powered by Stripe. Even if you have a Stripe account, you must create a new Oliver Pay account. You can use all the same business and personal information, but you will have a separate account and set of credentials to log in.
You can create a new account here:
https://partner.olivercdk.com/paysignup/
Go to your Stripe dashboard and make sure you're logged into the account that is managed by Oliver Pay:
https://dashboard.stripe.com/
Then navigate to settings > account details and retrieve an ID that looks like this:
acct_a1B2c3d4e5F6G7H9