Tap the Add collaborators icon at the bottom of the note.
Enter a person's name or email address. As you enter the text, you'll get suggestions to select.
Next to each name, click Done to add the person. Repeat steps 2 and 3 to add more people. Each person's profile picture will be added to the bottom of the note. To remove a person, click their icon, then click the X next to their name.
Click Save.