You can find the Text tool in the Brushes menu, which is accessible from your Tool Wheel.
- Open the Brushes menu by tapping an active tool or double-tapping an inactive tool on your Tool Wheel.
- Scroll through your brushes to find the Text tool, marked with an "A" icon.
- Tap the Text tool, exit back to the Canvas and then tap anywhere on the canvas to open the keyboard and start typing.