how do I change a text font to spanish character

usually, you set your whole system to a language, in the Sstems Preferences....

Then, via the alt- key on your keyboard, you hav access to 'local' characters, alt-o gives here a Danish ø, on English set keboards an umlaut ö.

alt-n gives a tilde ~, alt-n and another n gives a Spanish ñ ....

Experiment to find others like ® æ or 

or …

Open your System Prefs/Keyboard and check the lil' checkbox...

Tha gives a new icon in your menu-bar, which opens the list of characters (and the keyboard mapping):

there, you can pick up 'rare' needed characters

under the gear-symbol, you'll find many other type-systems to add, e.g- ≥ ♻︎ ⌘ ‰ Ģ

MacOS is multi-lingual ... maybe a bit 'hidden', ** it is 😀