If you regularly add photos to a particular folder structure, adding them to your catalogs is as simple as setting up folder watching and starting Expresion Media. Every time that you save media files into a watched folder it is imported automatically.
1. On the Edit menu, click "Folder Watching..." and set your update interval. (By default, the interval is set to "Never.")2. At the bottom of the Organize pane, right-click the folder you want to watch, and select Switch Auto-update on.
It takes both steps - but once that's done, no matter how you add files to the folder, they will be added to the bottom of the catalog. Keep in mind that folder updates include the folder you indicate and all subfolders. So make sure not to pick a top level folder unless you intend for all subfolders to be included.
Then you can use your metadata templates to add annotations - See Will's post below!