What is the error that you are getting?
To import documents into the repository, you should have a reference to DocumentServices as well.
This is a code sample from the documentation:
Dim document as New DocumentInfo(mySess)
document.Create("\Folder1\MyNewDocument", "Volume1", EntryNameOption.AutoRename)
Dim DI As New DocumentImporter ' DocumentImporter is part of DocumentServices
DI.Document = document
DI.OcrImages = True
The login, folderinfo, and documentinfo are all part of RA, but document import/export is provided by DS.