I currently moved him from Tucson, Arizona where he was housed in a very small trailer behind a house in very poor condition with no bathroom or kitchen and no running water. The person who he lived with continues to call him because they want his money. He gets confused and wants to go back. I need to get custody of him right away.
As to guardianship, you'll need to contact your local court, at a county level, to find out what the procedure is. You probably would be well advised to also contact an elder law attorney who has handled guardianships on behalf of others.
You will have to file a petition for guardianship, and the legal process won't be cheap. Do you have any siblings? If so, they'll need to be notified by the court and will have an opportunity in court to address your petition before any decision is made.
I'm curious though why you feel that custody is necessary - do you see this former roommate as a real threat, or do you feel that your father might decide to return to AZ without your knowledge?