font test

I am having troubles finding the answer to this (if there is one) but I am unable to find a way to change the font of the text in the help center article that I am working through. I copied some text from another document into this article and now the article has the default text font along with the font of the copied document. Is there a easier way to adjust the font of text that is already in the help center article? I understand that there is a way to adjust the font through the customize design but this doesn't seem to be what I'm looking for as this doesn't affect text already in the article.

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