"You appear to be running an X server; please exit X before installing."???

please exit X before installing
How can I do the instructions above? I am on Linux mint 32 bit 17.something “sarah” with a PNY GeForce GT 730.

Logout of desktop
login as root
kill Xorg
( NB: it might be just “X” so command would be: kill X )

There are other ways that depend upon the display manager in use as well as Linux Mint freatures. The above is general method that works for every distro that has virtual terminals set up, which is about 99.9% of distributions.

Fair warning: It would be best if you used the standard Linux Mint method of installing nVidia drivers. Installing via the *.run file is not a good idea for a newbie.
…but we all must learn sometime so if you want to try it, good luck!