open this page http://my-maemo.com/faq/showquestion...q=4&fldAuto=16 in your n900 browser then click on repositories you wish to add.
remove first what you done because clearly you done something wrong, which brings me to a question, should you be messing with such things if you can't figure out how to even add them? remember some software on there can be dangerouse to your phone so don't be surprised if you kill your n900