Just as you can restrict access to pages on your site to members you can also designate pieces of content within a page as only visible to logged members. To do this you use a shortcode. You can read about shortcodes and the things you can do with them here: https://en.support.wordpress.com/shortcodes/ The official description from the WordPress documentation reads:
A shortcode is a WordPress-specific code that lets you do nifty things with very little effort. Shortcodes can embed files or create objects that would normally require lots of complicated, ugly code in just one line. Shortcode = shortcut.
Member Splash adds several custom shortcodes. One of them is [MEMBERS-ONLY]. Any content placed between an opening and closing shortcode tag (the closing tag is denoted by a / before it: [/MEMBERS-ONLY]) will only get displayed to someone who is logged into a member account. Here’s an example of how to use it.