Steam has a remote download feature. When you're away from your computer, you visit your games page, click "download" next to a game, and (assuming your computer is on) it will start downloading.
However, it always installs to C:\Program Files\Steam. C: is my SSD - I don't want games installed there.
Is there some way I can choose which folder to default to?
It doesn't look like it. I just tried installing Bioshock Infinite from my phone, and it didn't give me an option of which library (I have 2) to install to. It looks like it will install to the default (i.e. the first) library.
If that isn't the library you want to install it to, then you can always move the game after it finishes installing.
It doesn't seem like you're able to change which library is the default either. If you want to change which library is the default, you'll have to reinstall Steam onto the drive where you want your default library.
