For the user the block works like that: The user sees, that he can find for example libraries, that are near to him/her. So the user enters his/her address in a text field and the nearest libraries will be found and shoen on a map. The nearest library is shown first in the list.
As administrator you find a link in the Simple Map block to upload and edit the places, that should be shown on the map. Click on that link. You have to upload a csv file, that is exactly as described on the upload page. Most fields are optional. You do not have to give the latitude and longitude coordinates, they are calculated automatically for you, so leave them blank, if you don't know them. But you have to fill out the address.
You can also add places manually instead of uploading a CSV file.
For customizing the block further you can contact us at http://www.edulabs.org