First, install Windows 7 onto the SSD with only the SSD connected to the system.
After you have Windows 7 fully loaded. Shutdown, then reconnect the HDD. Once connected, power on the system. Windows will detect the HDD as a new device and install it. Then you can format it if desired.
Always make sure the system is shut down (powered off and power cable disconnected) when connecting/disconnecting items. Also, the easiest way to disconnect the HDD is to simply remove its power connector.
Got it now? Good job on asking questions for clarity.