Here are the steps to draw in iMessage:

1. Open the iMessage app on your iPhone or iPad.
2. Tap on the recipient's name to join with iMessage conversation.
3. Next, tap on the heart icon near to iMessage text box.
4. Start to draw on black canvas.
5. To get a larger canvas, tap on the upper arrow icon at the bottom right corner of the screen.

You can also use Digital Touch to send animated sketches, taps, kisses, heartbeats and more . Here's how:

1. Open or create an iMessage.
2. In the App Bar (also called the App Drawer), find and tap the Digital Touch icon.
3. In the Digital Touch window that appears, tap the color dot on the left side to change the color of the ink you're using.
4. Then use your finger to draw your sketch.