Changing the text within a text box or text groups can be done by selecting the text box on the template. Then type in the desired text.
Make sure the text box is selected before typing or pasting text. You can also delete the existing content by highlighting the text and pressing Backspace or Delete on your keyboard.
If you already have an existing document outside of the software with your text, you can paste copied text from an external source (e.g. word documents, web pages, PDFs, etc.) with the
Ctrl or Command + C = copy
Ctrl or Command + V shortcut = paste.