It looks like your on the right track.
You made an item and are trying to add it to the Dragon scripts if I am reading your question correctly.
The scripts are very simple and all you really need is to add the item number that you have added into the UO files. Item numbers are the second column of numbers in the scripts.
If your asking how to add items into the UO files to add into the Dragon scripts you will need to check the forums for the actual steps. From your post it looks like your French(?) so the following links might be more helpful.
http://la-croisee.net/
http://uo-graphics.uo-francophone.net/index_fr.php
Best of luck and hope that helps.
Dev