If you mean how to add text to create a text embosser/debosser, you would do that in another app like an image editor, save to PNG and then upload that to Cookiecad. Here is a guide on how to do that: How to create a 3d printed text embosser / debosser
If you mean add text labels onto the side or bottom, here is how you can do that after downloading the STL How to add text labels to your cutter STL using 3D builder.