First, I hope you will take care of this in the weeks before your wedding. Decide which newspapers you want to send your announcement, contact them or visit their website for pricing and publication deadlines, and write your wedding announcement. Even if the newpaper has a form, I suggest you supply your own copy of the announcement. They will edit it, if necessary.
Here is a basic format to follow for your announcement. It can be tweeked in lots of different ways depending on the size of the announcement you are purchasing. See notes following the basic form for suggestions.
It starts with the who, what, when, where.
(Your names) and