At the first time you need to know that screen sharing is called "Meeting" in TeamViewer. You / the presenter needs TeamViewer full version or TeamViewer Portable. Others / viewers needs only thin client TeamViewer QuickJoin. All of these apps are free for Windows, Mac OS X and Linux and can be downloaded from https://www.teamviewer.com/en/download/.

Before you start your first presentation you must go to options and set up your meeting. Go to Extra, click on Options and switch to Meeting. After this you can see window from this picture.

In display part if you don't know how good is your Internet connection then use Automatic quality selection else if you have good upload to Internet then use Optimized quality else use Optimize speed. If you wish to show your wallpaper to viewers then uncheck remove own wallpaper.

In meeting defaults part select Minimal interaction (viewers now can't interact with your screen). If you wish to share your screen with your music, etc. check share computer sounds and music.

After all click on OK button, switch from Remote Control to Meeting and host presentation meeting.