OK, with your code, you're formatting the whole document with 12pt bold text, centred paragraphs. Is that what you really want?

It is always better to use appropriately-defined paragraph Styles for managing document formatting, rather than overriding an existing Style with the format you want.

FWIW, to insert another paragraph is as simple as adding another line with:
.InsertAfter vbCr & "My New paragraph"
Then, of course, you'd want to format the new paragraph, for which you could use code like:
.Paragraphs.Last.Range.Style = "Some Style"

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