U can add as much storage as u want as long as there are SATA connectors for them.
While a typical storage device come pre-partitioned and pre-formatted and immediately recognized by Windows, sometimes they do not, so this is where user intervention is required, so sorry this is not easier.
First thing u have to do is, DOES BIOS RECOGNIZE IT? what the dicken that means? You boot into BIOS, don't boot Windows just yet, and one of the BIOS screens u should see ALL of your storage devices. U must see them here else nothing is going to work. Don't see it here, something fundamentally wrong. DOA, bad cable blah-blah.
Once BIOS recognize it, then you boot into Windows normally, and again if God is on your side it's all pre-partition and pre-formatted and Windows automatically assigns it a driver letter. Don't see this, then you have to fire up DISK MANAGEMENT and do the partition and formatting yourself. What the dickens does that means? Gosh we can spend a whole day here holding your hands or you can GOOGLE INITIALIZING STORAGE MEDIA.