How to read inputs from file (please read the details before answering)?

I have learnt recently how to use fgetc, fputc, fputs, fgets but still I am not able to figure out how to read values from a file like for example:
12 14 1928 32993932
17 98
166 109 201
These are separate integers & i want to read them and then manipulate these individual integers like going for 2*I1, 4*I2 and so on where I1 and I2 are 12 & 14.

Tell me if I need to study something or have to know something more, please share link if possible.

> where I1 and I2 are 12 & 14.
So where do l1 and l2 come from later - more user input?

And in this lxxx naming convention, what would 98 and 201 be?

Look, these inputs have been given in any .txt file - I just want to read them and then manipulate them as per my usage in a program.