enter your information and confirm through the link you get in an email. Then you have to fill in you profile as much as possible so your potential job offer can reach you - Education, work experience etc. Then you need to invite your co-workers and friends and link with them, as you build your professional network, you will be able to reach an be reached my many HR and recruiters in case you need to find a job. You can also sign for various professional interests groups and communicate with people who have similar professional background. You can also endorse skills of the people you worked with and they can endorse your skills.
The value is to be able to reach and be reached by many professionals in your area and HR managers in case you need to find a job, and also to be able to recommend and be recommended.