petitions to the Holy See
All the faithful are free to request favors from the Holy See but where one's own ordinary is empowered to grant them it is advisable to seek them from the Ordinary.
The Pope can be approached directly; however it is customary to address him by means of a petition presented in writing to the particular Roman Congregation whose province it is to grant the favor in question.
And it is always well, and frequently even necessary, to present a letter of recommendation from one's own Ordinary.
New Catholic Dictionary