The quickest way to create a new graph is to use one of the templates as a starting point. Import the data by dragging it onto the table or by selecting “Import...” from the Data menu.
The templates are just starting points, and not separate drawing environments. The same graph can easily be created from scratch. To change the column type, the quickest is to use the context menu for the column (control-click or right click). This allows you also to set the x tick marks to be categories, and based on this column. When you open up the axis settings you will notice that the “X tick marks” are now “Categories” and the “Label” column has been selected as labels.