I'm imagining one of those "choose your own adventure" type books I used to read as a kid.
I'd ordinarily advise against starting something like this on only your second day, but you seem to realize this, and I certainly don't want to discourage someone who is eager about learning and creating.
I'm also sure that you're aware that, if you continue to learn, you'll be able to do a project like this much easier by mixing the various basics (writing functions, "switch" statements, loops, etc) instead of just if-else statements.
However, it can be done with if-else statements - although it will be ugly and limited. Also, unless you're familiar with loops, you wouldn't be able to pick a piece of story that preceded a current one (which can easily happen in these types of stories).
Definitely map it out on paper, as you mentioned. You might want to consider typing up each possible block of text and assign a number to it, as well as the associated choices and which numbers they would branch to. This way each one will have its own identification value, which can be assigned to the input variable when that choice is selected.
Code:
// pseudo code
if(input is 1)
(print first message)
(does user want to do (2) something or (3) something else?)
if(input is 2)
(print something)
(more choices)
if(input is 3)
(print something else)
(more choices)
// etc
Also, you're assigning numbers to variables (a, b, c) that don't appear to change their value, and are just used for comparison. Why not just ditch those extra variables and compare the user input against number constants:
Code:
// what you have
char a = 1;
char b = 2;
char c = 3;
int answer;
scanf("%d",&answer)
if(answer == a)
// do something
if(answer == b)
// do something else
if(answer == c)
// do something different
Code:
// what might be better
int answer;
scanf("%d",&answer)
if(answer == 1)
// do something
if(answer == 2)
// do something else
if(answer == 3)
// do something different