Just to curb any miss understandings. Your notebook has a 1TB Hard drive and 6GB of memory. RAM is Random Access Memory. We commonly refer to RAM as just memory. When your System Information says you have 5.89GB Usable it is refering to the total ammount of RAM that Windows can use after reserving a little bit for the graphics processor and/or other low level system stuff. If you want to get a better view of how much RAM is being used at the moment open Task Manager. CTRL+SHIFT+ESC is the shortcut to open Task manager, or you can Right Click the Windows Icon (8+). If you really want to dig into what is doing what you can open the Resource Monitor.
It sounds like you have a pretty nice notebook. However HP sometimes puts slow HDDs in their notebooks. With HDDs bigger is not always better. I would guess that it is usually more advantageous to have a faster hard drive than a bigger one. I recommend replacing that 1TB drive with a solid state drive. 250GB~500GB drives are afordable and stupid fast compaired to the drive in your notebook. Applications will start up faster and you will get more life out of your battery. It can make a three year old notebook feel brand new and make a newer notebook feel like a hot rod.
Have fun 🙂