I was able to figure this out for you.
Click Home
Click the little arrow to choose numbering style
Click Customize numbering
Choose the Sequence style and the Format
Type your content then press Enter
then Backspace
then Tab
Choose format for next section
To create a sub-section to the sub-section, press Enter
then Backspace
then Tab
Continue the sub-section.
To go back to the previous section, from the content line press Enter
then Backspace
twice
Continue that section then to return to previous section, from content line press Enter
then Backspace
twice
To go back to first section press Backspace
twice again
Continue your section from there
As far as changing the numbering to 1.1, 1.2, 1.3, etc. I don't think you can. You have to choose from the predefined formats. You can choose what number to start at though from the last option on the Customize numbering
window. I tried changing it to 1.1 and 1.2 but it doesn't stick