User Permissions SQL Server

db_owner
Members of the  fixed database role can perform all configuration and maintenance activities on the database, and can also drop the database in SQL Server. 
db_datawriter
Members of the db_datawriter fixed database role can add, delete, or change data in all user tables.
db_ddladmin
Members of the db_ddladmin fixed database role can run any Data Definition Language (DDL) command in a database.

To change User permissions:

Database -> Security -> Users -> Properties -> membership -> add use to the required group