I have a boyfriend that lives in Ghana. I would like to know how can he obtain a visa to come here to visit. After the visit then he will move here.

It will likely be difficult for your boyfriend to obtain any visa other than a fiancé visa or immigrant visa. It is difficult to obtain nonimmigrant visas from the consulate in Ghana. You potentially have two options. The first would be a fiancé visa petition. One requirement is that you have met in person during the past two years. There is a limited exception of you cannot meet due to hardship or cultural/religious reasons. An exception is extremely difficult to obtain. The other option would be to marry and petition for him as your husband. Once you have married, you can file an immigrant visa petition on his behalf. You will need to establish was entered in good faith.   Each option requires you to follow a specific procedure and provide evidence regarding the relationship. One is not necessarily easier than the other. It is typically a matter of preference and eligibility.  You can read more about family immigration at http://myattorneyusa.com/family-immigration.