How to apply font ligatures to a text block – help required

I'm trying to replace the Karmina Sans letters "f" and "i" with the "fi" ligature. 

Please reference this page of my site where the "fi" ligatures are to appear: https://ivesgrafik.com/studio

I've attached examples of the Karmina Sans ligature screenshots.

I've tried copying and pasting the Karmin Sans ligature into the text block. A ligature appears; however, it's not the correct font.

Thanks.