The form with file upload field must be visible at the main page (not after click at some button), so, content object "uploaded file" must be created when the file is already uploaded.
Take a look at the content/upload module, it will allow you to upload content directly, and settings from content.ini will be used to determinate what class should be created based on file type.
Thank you for answer. I have understood how to upload a file, but there is question - how to add additional information about the file right after uploading, and how to link this information with uploaded file.
You can have object name and location as form values while uploading (browse to /content/upload to see form input names if you haven't already), normally you will be redirected to the uploaded file, and there you can have a edit button to let the user further edit the object(see for instance in the forum templates for how this edit button should be set up).
I want to view object edit form (to fill information about uploaded file) RIGHT AFTER upload.
And object must be published (or visible, as variant) only after user filled second form. Can I specify content/upload to redirect to object editing mode after the upload?
> Can I specify content/upload to redirect to object editing mode after the upload?
No, you'll have to create your own module / view for uploading to accomplish that, since content edit needs the object id witch isn't created before the upload is completed.