Here’s a quick review and some suggestions to improve clarity and grammar in your sentence:
Original:
> Tell us how this story idea come about (a great way to attract readers!).


Suggested revision:
> Tell us how this story idea came about (it’s a great way to attract readers!).


Comment:
The verb tense needs correcting—“come” should be “came.”
You might also clarify the parenthetical part slightly by adding “it’s” to make it read more smoothly.

Let me know if you'd like help polishing the rest of the text too!