Applying from US for B2 US visa for older people

Hi, Could you please tell how I can apply for my mother’s Visa B2 from the United states: what documents and where should i file the documents to get a B2 visa for 6 months for my mother. She is 66, she is retired and she is at her home country now. Myself, I am a green card holder and my application for naturalization is pending with USCIS.

many thanks