The beauty of joining a LinkedIn Group is you can now directly message any other member who's joined the group.  Start a conversation one-on-one with the individuals you admire and who you believe can offer valuable advice to help you through your job search.

Each group has a "Jobs" tab where you can gain information on the latest job openings.  Many employers, hiring managers, and recruiters will join professional groups on LinkedIn to help source talent and they will post any new job openings there.

Take part in the group discussions by posting a question of your own, providing an intelligent comment to other posts, or sharing relatable information with the group.  No one is going to notice you if you're just standing on the sidelines observing what goes on in the group.

As you consider what to post, comment, or share, make it relevant to your profession because it will help display your expertise on a particular subject matter.  It's not about leaving a generic comment or random post, but building on the personal branding message you 

 want to leave with people.