I want to travel from Ghana to usa,I have only passport,what else do I need?

Travel itinerary would be good as well, unless you intend to walk.
Also a valid entry visa.

If you hold Ghana passport, you must apply for US visa.

I see you are in Accra so here is a link to US embassy and visa info

Embassy of the United States Accra, Ghana - Home (http://ghana.usembassy.gov/)