I'll just guess that you're not too used to using the command line interface to install drivers in linux. So forgive me if I sound patronizing.
Ok, so you are using the 'command line interface' to install the Nvidia drivers? You will need to make sure that bash is working from the same directory that you downloaded the file to.
So, for example, if you downloaded the file to /home/user/downloads/nvidia.bin then from the Command Line interface you will need to type in these commands:
chmod 755 /home/user/downloads/nvidia.bin
And then press 'Enter'. Now, type:
And press 'Enter'.
If you still find this too hard to do then just say so and I'll help some more!
Hope this helps mate!