My boyfriend is a citizen of the Dominican Republic. What is the process to getting him to to the United States

You could apply for a fiancé visa petition. This will allow your spouse to enter the country for the purpose of marrying you and seeking lawful permanent resident. You will have 90 days to marry after he enters. Once married, he can apply for his green card. You can read more about the fiancé visa at http://myattorneyusa.com/k-1-and-k-2-visas-for-fiancees-and-derivatives.