If you go to the Research Guides page on the Yale Library website, you will notice that subject guides are arranged by academic discipline. 

When ready to publish a guide, chose from one of the subject categories available in the list.  

Do not choose more than 3 subject categories.  This is to avoid redundancies and make the page easy for users to navigate. 

Best Practice is to pick one or two categories only.

Do not assign a Course Guide to any subject categories.

Go to the pull down menu and select your subject disciplines. Remember not to pick more than 3.