@melmac cheers.
What games would you recommend for sitting down? Also, can I buy these games from Steam?
Edit: Also, what is the official download for the tray tool?
Others have already answered these questions

Yeah you can buy from Steam, I just buy from whichever store has the cheapest version of the game. I have spent so much time and money in getting my VR room setup that I am completely broke, so it's sales all the way for the next few months
What games would I recommend? Hmmm, I have pretty much enjoyed every game that I have tried. VR brings a whole new dimension to games, so games that you normally wouldn't play in normal mode become a whole different experience in VR.
Some games require you to have a strong stomach. Work on building up your tolerance or else some VR games will become a vomit inducing nightmare. The trick is to stop playing once you feel any kind of Nausea, don't try and fight through it. Eventually you will be able to play for longer and longer.
Here are some of sitting games that most people like
Alien Isolation VR
Blaze Rush
Land Fall
Chronos
I Expect you to die.
Sub Nautica
If you like Flight Sims, there is loads to choose and they work really well in VR.
If you like Driving games. Dirt Rally, assetto corsa and project cars 1+2 get well reviewed.
Elite Dangerous, if you like it, you probably have it already, if you don't, then it's probably not worth getting just for VR.
And I know this isn't a sitting down game and not sure if you like sport at all, but, Eleven Table tennis is well worth the cash. Even if you don't play it in real life. It's just so amazing as an experience.
One other thing to mention is The Lab, it's a free experience on Steam, it's not sit down but it's well worth checking out.
The Blu
Mission ISS
Ocean Rift
Apollo 11
Google Earth
Dear Angela
Face your Fears
Are also great experiences.