A LinkedIn profile isn’t just any old resume, it’s a place to showcase your best assets and successes. But with 300 million users on LinkedIn, there’s stiff competition! A great LinkedIn profile can help you have more success in your job, whether it’s being seen by a potential client, partner, investor or even employer. Make your profile stand out by adding rich media (videos, slides etc). Even just adding a profile photo could result in 14 times more profile views than someone without!
visit here

You can join LinkedIn for free, though you have to pay if you want a premium account, which puts you in touch with more people, job offers etc. Once you have joined - you can do this just by putting 'LinkedIn' in a search engine and then you will be taken to a registration page - you are given guidance in building up your profile.
The first part of this that anyone will see is your summary - a short snapshot of your career, usually with an indication of your main strengths. The longest section will usually be the Experience section, where you list past jobs, business experience etc. Then come parts like educational background, professional qualifications etc - quite similar to a CV.
Your profile should be as brief as possible, and you should look at some examples of good profiles before submitting yours - you can see some examples here.