I assume that you want to use Documents subfolder.
1) Place B4iBuildServer.zip into Documents and click it. This creates a folder B4iBuildServer. Move B4iBuildServer.zip to Recycle Bin.
2) Close Terminal, run it again and type:
cd /Users/administrator/Documents/B4iBuildServer
java -jar B4iBuildServer.jar
B4iBuildServer.jar will create additional subfolders and files, where they should be.