To get the necessary credentials you will need to log into Quickbooks. Then go to https://appcenter.intuit.com/Playground/OAuth/IA
Enter your consumer key and consumer secret into the two relevant fields (you can copy these from the Quickbooks consumer key/consumer secret boxes in MyExpenses (see below screenshot for reference)).
Change the value in the Access Token Duration to 15552000 (that’s six months in seconds).
Click on the ‘Connect to QuickBooks’ button. You should then be prompted for which company you want to connect to. Select the company you need to use the interface with.
Click any additional buttons required by the popup and the page will give you the additional OAuth details.
The OAuth details page will provide you with the access token and access token secret.
You will need to type these into the relevant boxes as seen in the below screenshot.
If you need to use the interface with more than one Quickbooks company then make sure you keep the other company credentials noted down safely somewhere and enter the new credentials.
If you have a test file available you can now check that the interface works as expected.