Click on the Breeding Kit to open it. Once open, you will see 3 buttons on the top row and 5 buttons on the bottom row. If no creature is selected, the Breeding Kit may autokill itself.
The leftmost button on the top row (egg button) will make the selected creature very fertile if they are a youth or older. The second button (two norns button) will age the selected creature to youth. The third button closes the Breeding Kit and returns it to its compact size.
The first two buttons on the bottom row have the same effects as the buttons on the top row, except that they work on multiple creatures. The next three buttons select the species (norn, grendel or ettin) that the first two buttons will work on.
Since the Creatures Mainframe is down, some of it's downloads are hosted here-->http://mandy.chani3.com/dsagents.php<--including the DS breeding kit.