Using the information packet provided with your FAFSA, determine if you are an independent student or dependent without considering your domestic partnership in that equation. The Federal government does not recognize domestic partnerships, unless they would be recognized as common law marriages in your state of residence, so your partner is not considered responsible for your education. If you do not qualify as an independent student by the listed terms, but believe you should be considered an independent student, the financial aid office can assist you in the process of asking for a professional judgment override -- the process wherein a student who falls in the guidelines as a dependent student can be declared independent.
Fill out the paperwork for the FAFSA for the dependency status you have determined. If you qualify as an independent student, fill out the FAFSA with your financial information only. Certain types of support from your partner, such as cash for things other than food or shelter, rent on an apartment or house paid in your behalf or utility payments on a rented residence, are considered untaxed income and should be reported on question 44(j) of the FAFSA. If you are uncertain about this amount or what should be reported, you can submit the FAFSA without that information and contact your school to discuss it with them, or contact the Federal Student Aid Information Center (federalstudentaid.ed.gov) for assistance.
Submit your FAFSA application either by mail, by hand to the financial aid office of the school you are possibly attending or online. If there are sections that you have been unable to complete fully because you have questions or aren't sure how they apply to you, submit the incomplete FAFSA form and contact the school's financial aid office to let them know you were unable to complete the form. They can make amendments to your FAFSA after you have filed the form and make awards based on those amendments.