I mean that the whole passage won't appear at once, but rather it'll appear line by line. I want it to be slower so that the story can be digested better but I'm having some trouble doing that.
You have tagged your question with all three built-in Story Formats but the answer to your request will be different for each one of them, so you need to state which you are going to use for your story.
Comments
SugarCube v1.x
Download the <<replacelink>> macro set from SugarCube v1.x's site (under: Downloads > Add-ons) and install it into your project. Then use its <<timedcontinue>> macro:
SugarCube v2.x
Use its native <<timed>> macro: