How to provide a access to the data base if the user is not having the privilleges
With SQL Server 2008 onward local Windows Administrators are not added as SQL Server Administrators by default.

If you do not have access to any Administrative account to SQL Server then you need to start SQL Server in single user mode, in this mode local Windows Administrators can login to SQL Server. Once logged in you can create a new Administrative Account.

Refer link for step by step tutorial: SQL Server – How to connect to SQL Server when ‘sa’ account is disabled