Are you wanting to add the text as free text to a layout in order to print or export to a PDF? Or how are you wanting to add your text?
In the Layout, you go to the Insert tab and pick from the Graphics and Text options on how you want to add the text:
Also, take a look at this:
If you are still having questions on how to do this, you will likely first have to insert a Layout. This link will help with that, then you can follow the instructions above:
You could also use map graphics if you need the text in the map view not the layout view. Learn more about map graphics here: https://pro.arcgis.com/en/pro-app/latest/help/mapping/layer-properties/work-with-graphic-elements-in....