This is where you enter the name of the conference as printed on the publication.
Examples:
International Congress on Mathematical Physics
Imaging and Cognition Genetics 2011
Annual Meeting of the German Society of Human Genetics (GfH)
If you do not know the full name of the conference, you can also enter the abbreviation that is commonly used on JaCoW (http://www.jacow.org/), e.g. "LINAC 14".