There are a couple of ways to get your books from Calibre to your tablet via wireless transfer.
If you're reading epubs, the easiest way to get them into your tablet is to use an epub reading app like Aldiko, Mantano, Cool Reader, Moon+ or FB reader to directly get the books from Calibre through its content server. You can browse your entire Calibre library from within the app and pick and choose which book/s to download.
Setting it up within the app is fairly straightforward. For instance, if you're using
Aldiko, to set up the Calibre content server:
1) Go to "store", hit the menu button and select "My Catalogs". Create a new catalog (hit the + sign next to my catalogs) and give it a name.
2) Insert this
http://youripaddress:8080/opds in the URL dialog (your ip address should be something like 192.168.1.XX - you'll find it in your computer's network properties).
3) Turn on Calibre's content server, turn on your tablet's wifi, open Aldiko, tap on your newly created catalog and you should be able to see your entire calibre library and download them into your tablet one at a time.
If you don't want to go that route or you have many many books to transfer over at once, you can set your Calibre library folder in your computer as a shared folder and then download a file explorer app such as
ES File Explorer from the android market and use it to upload the files from your computer.
Lastly, you can upload your books to dropbox and use either the dropbox app or ES File Explorer to grab them from the cloud as it were.
Hope this helps.
ETA: I realize now after re-reading your comment if you can't see your Calibre library through your tablet's browser via the content server, then most of what I wrote up there may not be relevant to you. Sorry!
