I am trying to reference labeled equations in a document but I am unsure if how to compile twice. Upon the first compilation I get (??) where all my references are. I followed this link: How to link an equation in LaTeX. I am using TeXworks on a MAC.
All that compiling twice means is that you basically need to run
latex latex_source_code.tex latex latex_source_code.tex
pdflatex latex_source_code.tex pdflatex latex_source_code.tex
in the shell somehow.
If you ever get into bibliographies you will need to run something like
pdflatex latex_source_code.tex bibtex latex_source_code.aux pdflatex latex_source_code.tex pdflatex latex_source_code.tex
This is all that running twice (or four times) means. How you place these commands into the shell depends on your editor/IDE. For TeXworks, this means you'll either have to manually click on the typeset button multiple times, sometimes switching processing tools in the dropdown menu, or use some kind of automation tool like arara (my favorite) or latexmk or rubber.
No matter what you choose, this should eliminate the