If you have located that you are running out of storage then all you have to do is purchase a new or external hard drive that has enough storage for what you require for example if you were working in something such as video production or photo shop then you would require something like 1 Terra bite of storage.

But if you were working with something such as documents or news you may prefer something such as 500 MB. You can get these at websites such as curry's PC world or Amazon, Ebay etc. 

They look like this in a computer.