Firstly the company and account number are the first part of the NetSuite URL for that client. For example if the URL is https://123456-sb1.app.netsuite.com/app/common/integration/integrapplist.nl?whence= then the company and account number would be 123456-sb1.
Next within NetSuite, go to Setup -> Integration -> Manage Integrations -> New. Give the integration a name, ensure that Token-based authentication, TBA: Issuetoken Endpoint and User Credentials are selected. Everything else should not be. Click on Save.
A consumer key and consumer secret will then appear in the client credentials section. Add these to the consumer key and consumer secret within the control panel key. These only appear once.
Next go back to the homepage by clicking on the house icon. Scroll to the bottom of the page and click on "Manage Access Tokens". Click New My Access Token. Select the Application that we just created and press save.
The Token ID and Token secret will then show up which can be added to the key.