To change the adress of a project or event, please select the project in the overview and select "edit xyz events": 

In the pop-up, you can either change a single event´s location by selecting an exisitng location or creating a new one by using the "+" symbol: 

If you want to change the location for more than one or all events, select the events that you want to change and use the location selector / add location "+" in the "Data" Tab: