First, go to 'Apps'->Integrations and then Cash Registers.

Click on Link new register, fill out the appropriate fields and create.

Click on the cash register you just created. Under the tab 'personal access tokens', you can create a new access token for this device with the button in the top right.

You also will need your account secret. You can find it under 'Apps'->'Integrations' and then find ‘account secret’.

Reach out to your Untill seller/provider for activation and provide them with the register personal access token and account secret.