you have a number of options open to you.
You can install your O.S. and all of your programs etc on the 1tb HDD ( Everything on the one Drive )
Partition the drive so you have say 200MB for your O.S. on one partition for example and roughly 800mb of free space on another partition for
all of your storage.
Or of you require speed for your operating system you could get a SSD for your O.S. and use your 1TB for storage
Or just use your 1tb for everything then if more space is required later on you could add an external drive for storage later on if you require
all of these methods will work fine