title: Installing LaTex packages in rmarkdown
body: <p>Can someone recommend a tutorial on how to install, add, and work with LaTex/MacTex packages in rmarkdown . For example how do you install packages such as amsmath and multline? Where do you go to look for the packages that are already installed? And do you have to install packages first and then call them in the document header or can you just refer to them in-text?</p>
  
  <p>I am incredibly confused and very few of the suggestions online work when I copy them, so I must be missing something absolutely fundamental but which nevertheless is not referred to anywhere online.</p>