I think your definition of "prompting" encompasses two things, and would therefore require two steps:
(1) Sending output to the user
(2) Receiving input from the user
Your original "printf()" took care of #1, so I would leave that in.
Afterwards, you want to put a command to look for a user input.
So right after that, you use the "fgets()" function. (it's almost the same declaration as "gets()", but much safer.) This will get a string from the user.
For the "fgets()", you want to look at the declaration of the function so you know what data to pass to it.
>> char *fgets(char *s, int size, FILE *stream);
You pass the address of the string in question to the "get string" function, and it returns the users input to the appropriate array.
You also have to include the maximum number of the array ("int size" is a limit to the expected characters, so the input buffer doesn't overflow) and the stream (stdin).