How do I enable the native share-to-installed-app function on iOS?

See the screenshots below. I have the Raindrop app installed on my iPhone and it shows up as an destination when I use Yelp's share function.

Step 1: Click Yelp 'Share' icon:

Step 2: Select installed target app to receive the shared info. In this case, Raindrop:

Step 3: Complete the share/save dialog provided by the target app.

Thanks in advance!