New To Rebelle. Tablet not working?

I just got Rebelle for the first time, so I'm totally brand new to the program and don't know my way around yet. When I Rebelle it with my mouse pad, the program works great, but when I use my display tablet, a huion GT-190, the lag is terrible. The lines are erratic and don't accurately follow the path of my pen. I'm on a Mac book pro retina (mid 2012). I only have 8 GB of memory, but I don't know if that matters since it works fine without the tablet. Is my tablet simply too old? Is it a problem with my computer? How do I fix this? Thanks!