I can see that there is not
Tahoma font in the document that I am currently working on.
How should add it, please?
In the font selector, at the bottom, is a link to "Add fonts...". Click that.
The "Add fonts" tool will open, showing all available fonts and indicating which ones you're using.
Simply find Tahoma (or whatever font you're looking for)...
...and click it so that there is a checkmark next to it. Click OK.
And now you should see Tahoma in your list of fonts while editing your document.