Shauna's page may be more than you think you want, but it will give you what you want, along with a stable numbering system. The thing is, it is all tied in together, at least it is if it is done properly. The buttons on the ribbon work fine for one-of documents that will not be heavily edited or shared. Not so much for documents that you will be using for a while. There is a technical term you do not want to become familiar with: spaghetti numbering. (For more on this term, Google "spaghetti numbering microsoft word.)

Numbering in Microsoft Word