what do i need to do to get my father to become a legal us citizen?

In your situation pertaining to applying for a father who has been caught twice by Immigration and has been in the US a long time, it is best that he obtain a copy of his entire immigration file and consult an immigration lawyer for an opinion as to whether his case can be done along with the lawyer explaining all the difficulties involved. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.