To “share” a post on your social media news feed on a desktop computer, click the button in the bottom right corner of a post. You have the option to “Share Now,” “Share”, etc. It is best to click “Share” because it allows you to share with commentary. Once you click on “Share”, the post will appear as if you are writing a new post. In this new post, you can add comments to the top of the shared post. Once done adding commentary, click “Post.” If you do not want to add commentary, clicking “Share Now” immediately shares the post on your page for your friends to see.
To “share” a post on your news feed on a mobile app, click the button in the bottom right corner of a post. The app will automatically show an area for you to comment on the post before you share. If you would like to include commentary, type in the blank space where it says “Say something about this…” After you are finished writing your commentary, click the blue “Share Now” button in the right hand side of the screen. If you don’t want to add commentary, just click the blue “Share Now” button without adding text.
Both of these processes are explained in more detail here.