Here's a simple way:
1. Format a paragraph that currently has the 'Normal' Style applied to look the way to want all numbered paragraphs at your first level to appear.
2. Click on Style>New Style and give the paragraph a meaningful name (the default will be 'Style1') and set the 'Style based on' to 'Normal'.
3. Change the format to the way you want all numbered paragraphs at your second level to appear.
4. Click on Style>New Style and give the paragraph a meaningful name and set the 'Style based on' to the Style you used for the previous Style.
Done

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]