So far, the experience of the iWork beta is one of the most frustrating I've had in 30 years of computer use. I've got an excel file on my Windows PC. I'd like to see if Numbers will successfully import, but there is no obvious way to open a file from the application. I don't necessarily expect all of the formulas to work, but no way to open a native file is silly.
I, too, am using the iWorks beta on my Windows PC. And yes, there is not much documentation. Well, none, really.
To upload a file, click on the Settings (gear-like) icon in the upper right of your PC's screen. The second option available is "Upload Spreadsheet." Clicking that line opens up Windows Explorer so you can find/import an Excel spreadsheet. This is the same process for importing a Word document to Pages and a PowerPoint presentation into Keynote.
They do import and, if you have iCloud turned on in the Settings tab on the iPad - you can view them on the iPad. Oh, and you're expectations are correct - they don't import perfectly. But - you'll see....
Marilyn
P.S. I've gone ahead and moved this issue of yours to it's own stand-alone thread. The one you posted in is so old and really, doesn't go with this brand new beta. So, I hope you don't mind. Maybe others will find it and we can give each other pointers on how to use this thing. I like the idea - just the implementation is difficult.