How to retrieve custom table data from sitefinity MVC projec

I am new in sitefinity. I'ld like to add some widget using custom development in MVC.

For some requirement I have to add some table inside the DB .  How we can retrieve this table's data inside the  MVC project.   I also need to access the user's information (i.e who logged into my sitefinity application for some business validation.)

Please help, how we can do that or provide some link.

Regards,

Ujjwal