The problem with job boards is that unless they are rather unknown, everyone is using them. Applying through boards is essentially like getting into the back of a line and hoping you get noticed.

When I coach job seekers on finding new work, I typically encourage them to be careful not to spend too much time on the boards, and instead rely on their networks/meetups or personal research.

Using LinkedIn to search for open jobs is similar to using any other site, but it's greatest value is as a research tool.

Say you're a Python programmer in a suburb somewhere and you're looking for a new gig. If you use LinkedIn to search "Python" and set a geographic preference, your results will likely be other Python programmers in the area. Where do they work? Where did they used to work? Sometimes LinkedIn will offer other profiles in the sidebar ("people also viewed") - click those and see where they worked. Now you've got a list of companies that have employed Python devs, so you can do a bit more research to see if they are the type of place you might want to work - and pay no attention to whether or not they have any jobs listed on their site.

Once you found some companies that interest you, use LinkedIn to figure out the best person to reach out to. Might be their CTO if it's a small shop, could be an internal recruiter or hiring manager for a larger firm. Make the approach, tell them why you're interested in the company, and make a soft close to try and get them to agree to a conversation.