Certain Blueprint videos have Spark moments where you can click on the Spark icon after it lights up.

The Spark icon lights up several times during the video when an idea or subject can be expanded upon. If that subject interests you, click the lighted spark and an activity will be added to your Spark Library for that topic.
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You get to choose how many lighted sparks you click on, which means you choose your activity subjects. There is no right or wrong amounts. Whenever something "sparks" your interest, click away.

After the episode, you'll see whatever topics you clicked on in your Sparks Library. Click "Explore" and you'll see all of your selected activities, with how many extra Spark points you earn by completing them.