“Main View” is a name whoever wrote the support article gave to their view. By default, a brand new table’s first view is named “Grid view”. If you want to change “Grid view” to say “Main View” or anything else, you can do so by clicking the down arrow and selecting “Rename”.
It is possible the help guide hasn’t been updated to reflect the location of the add view button since there were some UI updates. You create a new view in the view sidebar. Open the sidebar by clicking the circled button up top. And select the appropriate view type (grid, gallery, calendar, etc.)