The list of files in welcome window is a list of recent opened documents.

If the document you want to open is missing in the list, please open that file in the Finder with a double-click on its icon or use the button "Open..." in the welcome window. Then, the next time you launch iNotepad, your document should appear in the recent list.

Here's what a typical iNotepad document looks like:

You can move this file to the location you prefer in your hard drive and you can open it with a simple double click. If you do not find it, you can also search for it by entering its name in Spotlight.

Do your notes belong to an old version of the app? Take a look at this solution:

How to import notes from Notepad to new iNotepad