They've gone through some pretty major revisions of the user interface over the last couple of years. I have Firestick 4K devices but the UI shouldn't be much different.
IIRC from the old interface from the main screen you want to scroll across the top to the rightmost option and drill down from there. Under "Preferences" there are several options available including parental controls, privacy settings, location, time zone, and Language.
If the device auto-updated to the newer interface you would scroll about halfway down the main screen all the way to the right to the settings icon and from there step down and across to the Preferences setting and from that screen scroll down to the Language option.
Both US English and US Spanish are supported options.
Thanks. Last night I started fooling with it again. Decided to attach to a different HDMI port last night and could not believe my language got highlighted and selected by me. Now the challenger is puttin in the code for my WiFI. My network comes up, I select it, the board comes up to start selecting the correct numbers/letters, but I can't get the thing to move so I can select. Might try putting in a different HDMI port again. LOL.
I am determined to get this thing setup. Thanks again for the info.
Have a wonderful New Year!