Linux Mint is based on Ubuntu - I've been googling for confirmation that mint handles restricted drinvers the same way as Ubuntu as a result.
The howtos usually center around installing the latest
driver - which is not appropriate for all nvidia cards. The methods suggested involve obtaining the driver from the nvidia site - I understand their installer has improved.
The ubuntu method is to look in the desktop menus - System > Administration > Hardware Drivers - select the device you want to enable and - well - enable it. You usually need to be connected to the internet.
Method 2 is to enable the restricted (non-free, whatever mint calls it) repositories using System > Administration > Software Sources. Update with apt-get or aptitude - and use a gui tool like synaptic to search for the nvidia packages. Read the information supplied to determine which package includes support for your card - install it.
Method 3 - this keeps coming up on Mint searches - use envy
... this is an installation script which can be good for installing the correct nvidia driver correctly. Caveat: in general, do not run third party scripts - certainly google the script-name to find out if it is known to be bad for you. I do not like to suggest, even healthy, scripts because of social-engineering concerns.
Install the driver from nvidia only if (a) you need the absolute latest or (b) nothing else works.
You will notice that i is common for respondants to supply not-quite-enough information when you ask a question. This is a deliberate feature of the hacker culture behing much free and open-source software. It is a way of treating you with respect: you are assumed capable of figuring out what to do from the information supplied.
For instance, off me: "have you enabled it?" you are supposed to think: Oh - a special step is required that I didn't know about - so I probably havn't. I'll just google "enable nvidia driver mint" and see what comes up.
(Notice: the path to victory is usually embedded in the responce - look for the key-words.)
Hackers realise that not everyone is, or wants to be, competant in this way. Many people have other areas of competancy to maintain. However: gnu/linux's strength is in a growing and well educated community. It is in our interests to encourage even that small spark of skill we perceive in others - even when they do not see it in themselves.
So, if you feel stupid but find you are continually treated as intellegent - this is because we've seen the potential in you and want to nurture it. (Or - the answer you seek is too easy to find: we don't want to encourage willful ignorance