A show-reel is exactly that: a reel of your past work that you show to producers and directors in hopes of getting work. If you are a newbie, then you probably don't have past work to put into a show reel.
If you want to build your reel, then try and get with a professional editor or post house and begin working your way up through internships and apprenticeships. Once they start giving you some work to do, then you can start building your reel.
It takes time to build a reel, just like it takes time to build any decent resume with any job. Don't go out looking for big jobs or large paying gigs. Work small, offer to do some short films for free for any friends that you have. Take what you get from that to any post-production houses in your area, and ask if you can intern for free and learn the trade. Then, start building your reel.
