http://us.codejunkies.com/support/article.aspx?article_id=434 If you have a regular DS one
http://us.codejunkies.com/support/article.aspx?article_id=433 If you have a DSi
Or download from the link posted by Pokemon_Breeder_Moo and follow the same steps as whichever version of the code manager you're using.
Also, another confirmation from a newbie about v1.55 working.