Not a trusted SQL Connection

When you set up a sqlserver, there is an option that you must always set before any remote administrator can access to the sqlserver using "Sql Server Management Studio".

At the server where you install the sql server. Start "Sql Server Management Studio". (Assuming you have already setup sql server).

Goto menu bar View>Registered Server

Choose the local instance that you have setup previously and double click on it.

You can skip the above two steps if you can see the local instance in the object explorer already.

Right click on the instance in the object explorer and choose properties.

Select Security.

Under "Server Authentication", check "Sql Server and Windows Authentication mode".

Click "OK"

You should now be able to connect to the sql server from remote sql server management tool.