How do I go about getting fiance from Ghana to the US?

Significantly more information is needed in order to provide a legal analysis of ways your fiance may be able to attain immigration benefits, ultimately resulting in becoming a naturalized citizen, but generally when a foreign national abroad is engaged to become married to a U.S. citizen, an application for consular processing of a fiance visa will enable the foreign national to come to the U.S. for the purpose of becoming married within the required time. After that, the couple can go through the Adjustment of Status application process so that the foreign national spouse may become a Lawful Permanent Resident (get a "Green Card"). It would be wise for you and your fiance 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.