To access the Funding Circle API you will get access by going to the API Management page and generating an API ID and Password.
Working with Multiple Accounts
Each account has a different API Identifier and password. For example, if you have multiple accounts with Funding Circle (regardless of the type of account) you will NOT be able to use the same session token for all of the accounts. Instead, you will need to generate an API ID and Password for each account.
Authenticating with Version 2
Funding Circle uses session based token authentication for users to connect to our API. To begin using the API you will need to login using the API ID and Password that you have received from the API Management section of the investor portal (sandbox link) (production link).
For more information check out the Version 2 page here