Wedding announcements are published right after the wedding--within the first two weeks max.
Most newspapers now have a standard online form you can fill out for wedding announcements. When attaching a photo, be sure it is a high resolution jpeg that will translate well to print. Soft focus photos do not work as well as sharper ones. Your local paper can help you with the details
For ideas on announcement wording you can try these sites:
How to write a newspaper-ready wedding announcement
Writing the perfect wedding announcement
