All of the forms you need to fill out can be downloaded through the US Citizenship and Immigration Services website. You will need to file Form I-485 to apply for permanent residency, but depending on your eligibility requirements, you may also need to file other forms concurrently. The forms are detailed, and you will need to carefully fill out each section. A Houston green card attorney may also be helpful during this part of the process to ensure you have filled out every part of the forms required by the agency.