Notes App

The checklist icon doesn’t show up in my Notes app.

You have to to create your own checklist.

Read again -> Related Article -> Create a checklist with Notes

⤵️

How to create a checklist

1. Open the Notes app.
2. Tap the Compose button  to create a new note.
3. Enter a title and tap return.
4. Tap the Checklist button  to start the list. Each time you tap return, a new item is added to the list.
5. Tap the empty circle to mark an item as complete. 

To create a list in an existing note, place the cursor where you want to start. Then tap the Checklist button  and create your list.