I complete all the challenges and then I click code pen for completing my project but I don’t know how to use it.
Can you explain what you mean?
If I get what you mean then you have to copy this into your html file at the bottom:
<script src="https://cdn.freecodecamp.org/testable-projects-fcc/v1/bundle.js"
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What MrBondx said and also make sure you open js settings (little gear beside the js column) and set JavaScript preprocessor to “Babel”
babel is needed for react, it’s not always needed
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