Try the following:
Format>Bullets and Numbering>Numbered (tab)
Left click on a selection that looks closest to what you want.
Left click on the Customize... button.
In the Customize Numbered dialog, in the Number format section you'll
probalbly see something like the number 1 with a gray shading and a period
after. The grey shaded number is what increases in the list. In order to get
a list like you describe, place the cursor in the Number format text box in
front of the grey shaded number 1 and type the number 1 followed by a
period. Delete any punctuation after the grey shaded number unless you want
it to appear in your list. You can also control the Font, indentation, and
other formatting in this dialog. Click OK.

If there's any possibility your list will continue from 1.1, 1.2 to 2.1,
2.1, you should probably consider using the Format>Bullets and
Numbering>Outline tab. Good luck.

Bob