What kind of integration do you need? To accept payment on your website or else?

No , you can't connect to quickbooks app without client id and secret key

Hi there, Shane.

Allow me to share some details. All API concerns are handled on the Intuit Developer Forum page. 

You'll need to log in to get the answer that you're looking for. Here are the steps:

1. Visit http://www.developer.intuit.com/.
2. Click Help.
3. Select QuickBooks Sandbox, and click Ask a Question.
4. To continue the process, you'll need to either Sign in if you already have an existing account or Create an Account to create one.

If you need additional assistance with QuickBooks Online, never hesitate to reply to this post. Have a good one!