I need to develop a web application, for this my choice was: GWT+Hibernate+MySQL+Eclipse Helios, however, I'm not able to configure Eclipse with all those tools.
Is this combination possible? If yes, is there any tutorial for using them together? (I was searching on the Internet and I didn't find any appropriate tutorial) and concretely, how can I use Hibernate and make connection with MySQL database? (I created everything I need for GWT and now I don't know exactly how to call Hibernate)
In order to 'call' Hibernate you'll need to configure a SessionFactory using an appropriate datasource and mapping metadata describing the mapping of your domain entities to your database structure.
I suggest that you carefully read the Hibernate documentation before going any further.