You can use a Microsoft SQL Server client to connect to a DB instance through a common connection or an SSL connection. The SSL connection is encrypted and therefore more secure.
To connect to a DB instance through a floating IP address, you need to add the IP address of the target DB instance to the RDS security group. For details about how to create a security group, see the "Adding a Security Group Rule" section in the Virtual Private Cloud User Guide.
For details about how to create an ECS, see section How Can I Create and Connect to an ECS?
For details, see section How Can I Install SQL Server Management Studio?
For example, the following figure shows how to connect to a DB instance as user rdsuser.
If Encrypt connection is selected, SSL will be used to encrypt connections to a DB instance. (Encrypt connection is unselected by default.)