ASA style is based on Chicago. So, for citation managers (like EasyBib) that do not include an ASA style template it may be useful to format citations in Chicago style and then tweak them manually to conform with ASA guidelines.
Zotero: The Tri-College Libraries recommend Zotero, a free tool that can format your bibliography, keep your citations organized, and even save your articles in the cloud so you can access them later from the library, home, or a cafe. See the Tri-College Guide to Zotero for more details.
Any librarian will be happy to give you a tour or a few pointers of the software.