At it's most basic level it is a warning so you could just ignore it.
Or you can define _CRT_SECURE_NO_DEPRECATE (and from some sources _CRT_NONSTDC_NO_DEPRECATE as well) the best way to do this is by altering the project settings to include the symbols on the compiler command line.
Finally you could change you code to use the new (non-depricated) functions. However before you do that you have to be sure that this code is not portable and will never need to be portable, this is it will always only be targeted at the MS platform.
That is because these functions are only depricated by MS not by the C or C++ standards. While everyone agrees that the C runtime library has many insecure functions that could do with fixing their has been no consensus yet (as far as I am aware) on what the replacement functions should be. MS has just gone ahead and created their own (as have other people).
Anyway if you decide to change the code the clue is in the warning message, use fopen_s (this _s addition to the function name is common in the MS CRT for the newer secure functions, for instance strcpy is replaced by strcpy_s), the parameters are different so you will need to look up the function in your help (but pressing F1 isn't hard) and recode to the new prototype.