Printing the largest sum from integers in a file
Brad, you code compiles cleanly, which is a good sign :-)  Clearly it could be split into functions. An obvious approach would be to split the reading of the values from the processing of those values. 

I would take a slightly different approach, but remember there is no one "correct" solution. I would read and process the file
one line at time.  So the pseudo code would be:

    for each line
        read the line data  (function)
        find greatest sum in line  (function)
        store sum if bigger than max value found


This approach avoids the need for a multi-dimensional array and means you
  can handle an arbitrary number of lines.

Note that nested loops are often not desirable, but are sometime necessary.  Finding the greatest sum in the line looks like a case where a nested loop is optimal.  But this double loop should be a function.

Also check the return value from fscanf.  If you do this you can avoid processing a blank line.

A few comments on notation:


Be consistent!!!  This is important although it might seem trivial.  Many people
reading your code and seeing some places where a comma is followed by a
space (preferred) and some where it is not will judge the code badly.  Similarly,
comments should be consistent - follow // by a space. 
Defining just one variable per line is usually preferred.
Leave a space after keywords (if, else, for, while etc). Similarly,
leave a space before and after = (or != etc). (these are my preferences, others might differ).
Many people, including me, prefer code and comments to extend to no more than 80
columns. 
Send error messages to stderr and on error from system and library calls
that set errno (the global error variable) use perror (which prints to
stderr).
Exit on failure with exit(EXIT_FAILURE);
On completion, return a value from main, normally return EXIT_SUCCESS
Oh and finally, delete the useless comments. Nearly all of your comments are worse than pointless - they add noise, not information.