You generally create or edit a symbol from a part description in either a list of search results or a page like Favorites or a project. See “Searching for Parts”, “Saving and Accessing Favorite Parts”, or “Saving Parts to a Project”.
For more information about the IEC and JEDEC standards used by the PartQuest Symbol Creator, see the Custom Symbols section of the Account page (click Welcome, your_name, and then click My Profile).