Pink Elephant is wrong. It has nothing to do with anything being a "new client generation."
You just need to do it in a browser, and, based on your comment, of CMD + OPTION + I not working, I bet you're using safari.
To be able to pull up the inspector in Safari, go to preferences, then select the advanced tab, then hit the box at the very bottom that says "Show Develop Menu In Menu Bar"
Once that's done, go to the menu bar click 'DEVELOP', then click 'show web inspector' in the list, like in the pic. (Mine says "connect web inspector" yours will say "show". Hit it.
Then you should see something like this:
(It may be on the left side or right side of your screen. Regardless, next step...)
Go to the bottom where it says New Editor, click it, then click classic editor.
After that, select the text you want to change the font on, right click it to pull up the menu, then click "Inspect element" near the bottom of the menu.
Okay, now, after you do that, in the inspector, the very right column is going to change. The very top section of that column will show you the inline styles that are applied to the text you just inspected.
You'll see something like this:
Now, all you have to do is enter the font-family you want to change your text to, at the bottom of that box.Like this:
I added "font-family: Superclarendon" to the last line in the top box.
The font I inspected changed in the editor to that font.
Switch back to the New Editor and you're all set! Again, not all fonts work. The fonts in the list I shared are the ones that work for me. Not sure if those work on windows.