I am facing a problem sending credentials to another website so that I can login the user (automatically, not clicked on sign in here) and get an oauth_verifier value.

I want to send the email address and the password through a form (submit button) from my website (e.g. a Liferay portal) to another website (e.g. LinkedIn), so that it automatically returns an oauth_verifier to my website.
That means I don't want the user of my website to submit his email and password to LinkedIn again.
My goal is to take the email and password of the user in my website and show the user his LinkedIn connection, message, job posting (again, in my website, not LinkedIn). I dont want the user redirected to the LinkedIn website to sign in there and then come back to my website.
I have taken a consumer key and a secret key from LinkedIn for my web aplication.
I am using the LinkedIn API and getting oauth_verifier for access token but in order to login, I have to take user to LinkedIn to sign in, while I want it to happen in the backend.