The struggle to establish and maintain a file-based workflow on iPad is the white hot ball of anguish at the core of the whole debate over its usability as a main computer. So your question, seriously asked, is both perfectly innocent and painfully cromulent.
You can, but file browsing is a application that’s not necessarily accessible from within other applications. Your ability to use files, and external storage, will depend upon the apps you use and the exact details of your workflow.
