You can add both 2D Text and 3D Text to your effects in Spark AR Studio.
You can also let people using your effect edit the text you've included, by adjusting the text object's properties in the Inspector panel and adding a simple script.
This functionality won't be shown in the Simulator, but you can try it out on your device using the Spark AR Player app.
Click Insert, and select either 2D Text or 3D Text.
In the Inspector Panel, check the box next to Editable.
Change the Placeholder text to something that lets the user know they can edit the text, e.g. Tap to change me.
Edit the text's other properties, like color or size, if you want to.
Text will have been added as a capability automatically after being added inserted as an object.
You'll need to add the Touch Gestures and Native UI Control capabilities yourself.
Select Capabilities, and click + to add additional capabilities.
From the menu select Touch Gestures>Tap Gesture, and Native UI Control.
In the Asset panel, select Create New Script.
Find out more about the Native UI module.