Ubuntu currently won't use more than 4GiBs on my computer, but I need more space. My computer can hold much more than 4GiBs. How do I allow Ubuntu to use more? Please give step-by-step instructions in plain English.

Update:

I'm referring to my Ubuntu operating system. I installed it using Wubi through Microsoft Windows. I deleted Wubi from my Windows desktop after installation. All I want is to expand my Ubuntu operating system. I plan to gradually transition from Windows to Ubuntu and so I'll need to transfer more files and programs from Windows to Ubuntu in the future.

Right now, I already need more GiBs for Ubuntu. I can barely use Ubuntu right now because there's almost no space left. I simply want Ubuntu to use what space I need it to use. People, please quit complicating this issue and inform me how to make Ubuntu use more space.