How can I add new brush under User Defined

[MENIS]

Hello friends. I can't add new brushes to Brush. User defined doesn't open. How can I open it and add new brushes?

[Doug A Roberts]

There needs to be a brush library (or an AI file) saved to:
C:\Users\username\AppData\Roaming\Adobe\Adobe Illustrator 28 Settings\en_GB\x64\Brushes

for it to appear under User Defined.