I did a search and came up empty on how to use mathjax on this site. Do I need to use a third party or is a math symbols program built into the physics site?
This site has MathJax enabled, which means that you can essentially use any (reasonable) LaTeX command inside dollar and double-dollar signs (or indeed inside equation or align environments, among others), and it will display as mathematics; thus
will display as
For help in getting started with LaTeX as a way to typeset mathematics, the best place is probably the tutorial MathJax basic tutorial and quick reference on the Mathematics Stack Exchange meta.
You should not need any external tools to either view or write MathJax-powered mathematics on this site. If for some reason you don't see the mathematics displaying, you can ask here on meta but be sure to provide as many details about your browser configuration as possible.