To create a new API client you visit the API Credentials page on your account by following this link.
From here you click on the 'Plus' icon to create a new API Client
And then assign it the following;
Name - Keep it relevant to the application / third party that's going to be using it.
Link Expiry - If you want the reports to expire after a no. of days enter it here.
IP / Domain Whitelist - If you want to restrict the API to specific IP's or Domain's.
Permitted Scopes - The types of reports that you want the API to be able to view.
Visible Report Sections - The sections of a MotorCheck report that you want the API to retrieve data for.
Visible Spec Report Sections - The sections of a report that you want the API to retrieve data for.
Tip - If you don't want a specific section to show in the reports / certificates you retrieve by API make sure they are not highlighted in the Visible Report sections above.
If retrieving a Build Specs report you will want to have the permitted scopes and relevant sections selected as shown here.
Click Save and your API account has been created.
To view the OAUTH credentials click 'show' from the main menu and you will have everything you need.
For detailed documentation on how the API works visit this link.