There are a number of options for you to customize your Bibliography in the LaTeX template, however, some packages and methods may conflict with some aspects of how hyperref is configured.  If you would like to format your Bibliography and citation to match the natbib package, here are some suggestions to try:

• The first thing you should do is to add the \usepackage[natbib] to the preamble.
• Then you will need to select the bibliography style you wish the package to use. https://www.overleaf.com/learn/latex/Natbib_bibliography_styles  
• You may need to add some customizations in the preamble to have the in-line citations work as you intend. https://www.overleaf.com/learn/latex/Natbib_citation_styles
  • For instance, using:
    bibliographystyle{abbrvnat}
    \setcitestyle{authoryear,open={(},close={)}}
    ...will alter the brackets in the citations and produce an author/year format.
• There may also be some other edits that need to be made to get everything in order, but make sure that your syntax is correct in your bib file and that you are using the right declaration for the style you want to use.

If you aren't able to make the Bibliography render, please contact ETD Support or use the Contact Us button in Overleaf.