If I am the primary sponsor but I don't have a job or income, how do I fill the I-864 form?

In a family-based immigration application the U.S. citizen sponsoring relative must provide an Affidavit of Support. If he/she does not have income, then that information must be accurately stated. You appear aware that when the sponsoring relative has insufficient documentable income it can become necessary to have joint sponsor, and if your father is a U.S. citizen or Permanent Resident, he has sufficient documentable income, and he is willing to assume the responsibilities associated with the Affidavit of Support, he can qualify as a joint sponsor. Of course, there are many other details that impact immigration eligibility. It would be wise for you and the foreign national you are sponsoring (your spouse?) to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.