This article explains what steps to take in order to use the Open API
You must be a LendingWise client to fully use the API.(If you are not, please Sign up here to create a LendingWise account).You can explore the OpenAPI docs & use sample credentials provided to test and see the data output.
First you must confirm if what you are trying to accomplish cannot be accomplished with the API-Lead Data Posting or Webhooks. If it cannot, then you can request access to the Open API by submitting an "API Related" help ticket here: Submit a Help Ticket to request API access to your data.
There are several endpoints but the most important will be “file” and “files” endpoints. “Files” will fetch all loan records that match your desired query with around 30 data points. The “File” endpoint will fetch up to 400 data points within a single loan. For technical help or to request additional fields in the API please Submit a Help Ticket.
The first step is to put your Client ID, Client Secret and the API URL in a configuration file for your code. These are the only three pieces of information you need to access the API. You can use "test" for the Client ID and the Client Secret to get a Bearer Token you can use to test the API and get back sample data structures.
Please see this article in regards to the OpenAPI.