To use the User Logged In Shortcode and insert it into your content go to the course or page where you'd like to use it.
Click the eLearnCommerce icon in the editor and select Miscellaneous -> User Logged In.
As you click it the shortcode will be added to your editor.
What this does is that all the content that is between those two Shortcodes is visible to Logged In Users only.
You can use this to communicate with a user that just logged into your Membership Site.
To know more about eLearnCommerce's Visual Shortcode Builder, click here.