ow to add a new instrument

Hi,
I cannot use new instruments from external soundfont (Mac OS Mojave, Musescore 2.2.3)
This is what I have done so far:
Download .sf2 file
Right-clic in the file, run the file with musescore
musescore tells the soundfont was installed
Go to the syntetizer, mount the new soundfont in the curent staff
Change instrument in the current staff
This is where things went wrong: the new instruments are not accessible, neither in the list nor by typing their name.

Thanks for helping.
Please try to be specific. Do not redirect me to online helps or tutorial since I already followed several of countless number of times before I decided to post this message.