So you have just installed Linux and you want to make sure everything is working?
I have a few steps to make sure your GPU is in full use.
First I install Screenfetch in the terminal
sudo apt install screenfetch
Then type screenfetch in the terminal and the output will look like this
Now check and see if a GPU is listed, if it is good you are all sorted, if not lets keep going.
Now in the terminal type;
sudo apt install nvidia-375
After the install which is around 375MB reboot your pc, run screenfetch again and your GPU should be listed!