If you configure an ‘address’ field in the MapPress ‘geocoding’ section, MapPress should automatically create a map when the post is published or that field changes.
If you don’t see that map, check that the field is actually populated – often this question comes up because people are using a custom fields plugin or theme that doesn’t store the data in a custom field.
To tag posts I’d suggest using tags or categories. There are examples in the documentation about how to query by tag/category. You can test your query with the mashup shortcode, and one it’s working just enter that same query into the widget ‘query’ field to get it in the widget.
If that doesn’t help please be more specific with your question and, if possible send a login to the blog using the contact form.