Create first some headlines and some of them should be Heading 1. Place the mouse marker on a headline that is Heading 1 and click on the button in the page below. Choose in the Paragraph menu the Multilevel list. This will create a numbering where the main headlines (Heading 1) have whole numbers (1,2,3…) and the sub-headlines are numbered with something that resembles decimal points where the first number comes after the main headline (1.2,1.3,1.4 etc.).