By default, any content hidden using either registration walls or paywalls will display a "Read More" button that indicates hidden text. Clicking on this button will load a pop-up prompting users to register or pay to access the premium content.
If "Read More" isn't appropriate for your community's content, you can change this from within the Publisher dashboard.
The site interaction page under settings will display a section titled "Article Lock Button Text". You can change this value to customize the read more button across all instances of your Pico account.
This is a global change; if you want to edit individual pages or have more control over hiding and showing content than the default behavior, consider using Pico Signals.