You will get the options to change your connection while adding the object's go to report editor > add tables or add images then you will get the pop up window to choose the object and to the right will get the option to change the connection .
NOTE: In the connection tab, un-check the use as default connection option
It appears that you want to use the Linked Fields functionality of NPrinting. Here are the links to the tutorials for setting it up with version 16. This is done through the sources option:
Hope that gets you moving forward. If you are using version 17, there are similar tutorials available on the Community for those too.