1) See if there are any local programming standards you have to follow. Indentation, style, portability, licensing, compiler options. Maybe there is a template you can use as the basis for your program.

2) Work out the rough structure of the program - what does it have to do, how does it stop. Write it down.

For example
Code:
This program must:

Print a hello message
read a line of input from the user
while the line of input is not empty
   respond to that line of input
   read another line of input from the user
Print an exit message
You should able to use a search engine and a bit of intuition to work out how to do nearly all of those steps in the C programming language, apart from maybe the "respond to that line of input". Maybe when starting out assume that the requirement is to just print "The user entered '.....'", so you can check that works.

You will then be at the point of inspecting the user's input and acting on it.

3) If you get here, now you will want to work out how to 'parse' the user input to see if it is valid command, then act on it. When you get that far, come back and ask for more direction.