File manager?

Here's my problem:

I currently use my iPhone or iPad as my personal computer. I've come across a few websites where I need to attach a file before finalizing the submission. So on the page there is the option to browse my computer to locate the file that I would like to attach, but of course I'm not using a computer. I need help!!! Is there a way to browse the files to attach the file I need or is there an app that would allow me to do this?!?

 

This may be a stupid question, but I've done the iOS 6 update and still having the problem. I think I might need step by step directions or suggestions?!?