Problem compiling PDF file

I'am working with a new Shell, and after I had installed it I can't use it because I can't compile the PDF.

The main problem is as follows:

Package natbib Warning: Citation `bagby03' on page 3 undefined on input line 17
9.
LaTeX Warning: Reference `s:intro' on page 3 undefined on input line 195.

 

How can i solve the problem?
 

Thanks!!

These are routine warning

These are routine warning messages during a first compile pass, or if you are using BibTeX and haven't generated the bibliography.

A LaTeX error starts with ! followed by the error message and then the line number and a fragment from the LaTeX script where the error happened.

Post the error message, or better yet the entire .log file.  Depending on the error, the .tex file might also be needed to locate the error.

I think I solved the

I think I solved the problem! Thanks anyway!!