You need to register the ereader with kobo to use it.
If you do not plan to buy books from them use any email address and bypass payment information. You can do this using WiFi connection.
You can also bypass registration following information in thos post (is the same for Aura):
https://www.mobileread.com/forums/sho...88&postcount=7
No need for Kobo Desktop at all.
To copy books to your reader use Calibre or copy them to root folder in the eReader. I think you can also put them in folders, but do not copy too many books at a time or the ereader can became "stuck" trying to index all of them.