Hi,
If the posts are all assigned to a specific category/tag the easiest way to do this is to use a mashup for that category/tag with posts_per_page=-1. There are some examples in the documentation:
http://mappresspro.com/mappress-documentation
If you don’t know the category/tag being in advance I’ve recently added a way to include the URL request variables in a query. Just prefix the variable with ‘@’. For example, to show all posts in the current category use:
[mashup query="cat=@cat&posts_per_page=-1"]
I hope that helps!