A text button is a button with a word in it. To add a text button, you edit a button section by clicking on the cog icon next to the section in the layout sections portion of the builder. If you don't already have a section, click on the add section button and select the buttons section type which will add a text button at the bottom of the section list.
Once you edit the section, you will see something that looks like this:
Click on the add text button button to add a default text button that is labeled button.
Click on the button button (the new button that you just added) to edit it.
Here you can override the color and specify what action you want the button to have. Change the label to whatever words you want in the button. For example, if you want the button to say HELP ... change the label field from Button to HELP.
If you decide that you no longer want this button, you can press delete to delete it.