How do I file a green card for my mother in Nigeria?

Significantly more information is needed in order to advise about eligibilities, options and strategies for your mother. For example, are you a U.S. citizen? a Permanent Resident? a nonimmigrant foreign national? What is your mother's immigration-related history? Etc. If you are a U.S. citizen, you may be able to petition for your mother and successfully complete consular processing for her so that she can become a Permanent Resident (get a "Green Card"). There really is no substitute, however, for you and your mother consulting with an immigration attorney about this.

You start with the form I130 and instructions to it.