The easiest way is first to connect the pc only with the SSD and complete the windows installation. Meaning disconnect your old HDD(this is to remove confusion for noobs)
Do not forget to set the SSD as your top priority boot device among other HDDs in BIOS.
After you are done, reconnect the HDD and just format your old Win7 installation...and you are all set...
Usually I prefer to have a fresh install of Windows for every new HDD/SSD which is planned for system.
There is another way, which is to clone your Win7 partition move it to SSD and adjust several things...but this is not noob friendly and I prefer to have a clean fresh install