Me & my future husband want to get married legally. However he currently lives in El Salvador and I live in the US. What can I do so he can come here

You could file a fiancé visa petition on his behalf. This would allow him to come to the United Stares for the purpose of marrying you and seeking permanent residence.  The other option would be to marry outside the United States. Once married, you could start the immigrant visa process.  You can read more about both options at http://myattorneyusa.com/family-immigration.