We provide free instruction on setting up Linkedin API Key and LinedIn Secret Key.
1) Go to LinkedIn developers link and login with your credentials. Click on the "Create App" link.
Fill form fields and click Create app button
Go to section Auth section
and
fill Redirect URL:
http://www.yoursite.com/module/MODULENAME/linkedin
You will get Linkedin Client ID (API key) and Client Secret (Secret Key)