This is possible for authorized users only.
Choose in the menu "Import", then "Addresslist". Now it's important to use the right format and colums in a excel sheet to successfully import the new addresses.
You see on this side all the requested columns and with the blue textlink you can download an excel template. Every column is needet and also the order is important (but you do not need to fill out every column).
After filling out this excel template, save it to your computer. Click on "File Upload", select the excel-file, then cklick "Import". Now you get a report of the import proccess. In case of a fault you see what's happend and the procces will stop. Correct the fault and try again, already imported lines will be overwritten.