When I first got my N810, i had to flash with newest software which at that time was 2007.50-2, after that i just opened skype and it installed automagically, the only thing i had to do was to accept the EULA. I hope this helps you.

If you are using windows you can get the flasher software from Nokia here: http://tablets-dev.nokia.com/nokia_N800.php Just follow the instructions and you should be good.