Create template with linked numbering

[Kris-I]

Hello,

I use Word 2010. I'd like create a template. The starting point is the default template. I'd like change (or create new style) Heading1, Heading2 and Heading a numbering, the numbering must be linked.

The format should be :
- Heading1 : 1
- Heading2 : 1.1


- Heading3 : 1.1.1

I tried to create a "new multilevel list" but I don't know how to attach the different level to the style (Heading1, ...) or I don't know if Im' on the right way.

Thanks,