In SQL Server go into security under the username that you connect with and that Kentico uses to connect to the db with and make sure it owns the db_owner and/or dbo schema, remove any additional schemas it owns.
You will then need to run some sql to drop the tables that you do not need and then use the SQL AlterSchema command to change the db owner. By running the below script you will get the results of all the tables, just copy and paste that into a sql window and execute it. (replace 'Charles' with the schema owner you want to change).
SELECT 'ALTER SCHEMA dbo TRANSFER ' + s.Name + '.' + o.Name
FROM sys.Objects o
INNER JOIN sys.Schemas s on o.schema_id = s.schema_id
WHERE s.Name = 'Charles'
And (o.Type = 'U' Or o.Type = 'P' Or o.Type = 'V')