Adding a "find out more" box to posts in wordpress

I am trying to figure out how to have an option for a “Find out More” box inside posts. a box where we could put links, etc, to find out more about what is in an article. Kind of like the way the block quote tag allows you to highlight certain text, but more removed – like an actual box, within the post. Does anyone know how you can do this?

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thanks!
Jacks