Configuring only games to use the NVIDIA GPU - Ubuntu 18.04.2

I’m completely new to NVIDIA X Server Settings, and I want to ask the community how to do this before I try to do something I’m not sure about.

On my laptop, I run Windows on one partition, Ubuntu 18.04.2 on the other. On the Windows partition, I have graphics-intensive programs (Like Blender and Minecraft) to run on the NVIDIA GPU and everything else to run on the Intel GPU. The graphics (At maximum settings) run smoothly on the Windows side.

I tried launching Portal 2 the other day, and it was fine up until I tried getting into one of the test chambers. It was SO SLOW and VERY choppy. I know that there is a power-saving mode in Portal, and it was disabled.

For now, I set the PRIME profile to use the Intel chip by default.

So, how can I let certain programs use the NVIDIA GPU?

Thanks in advance.

For the moment, this would require installing/using bumblebee.

And how/where can I get bumblebee?

Please see this:
https://wiki.ubuntu.com/Bumblebee