Although I think Livestream can work with other brands of streaming software, their own streaming software is called
Procaster. It's what I use for my Livestream. It's free and available both for PCs and Macs. It can sometimes be a little demanding and memory-heavy on your computer though, especially while running other large programs like Photoshop or Firefox. So if you have an old computer, you might run into some problems with that.
Once you download it, it's pretty straightforward. Sign into your account through the Procaster program, poke around the settings options to set up things like your video resolution and file saves, and you can be on your way.