cinderella
The Yehi Ratzon is found at the end of most sifrei Tehillim and is said only after completing at least one sefer of the five, which correspond to one of the Torah’s five sfarim.
The 150 kapitlach are divided into 5 sfarim:
1. Sefer Rishon- 1-41 kineged Braishis
2. Sefer Shaynee- 42-72 kineged Shmos
3. Sefer Shlishi- 73-89 (a short one!) kineged Vayikra
4. Sefer Revii- 90-106 (also short!) kineged Bamidbar
5. Sefer Chamishi-107-150 kineged Dvarim
There are two Yehi Ratzons: one for weekdays and a shortened one for Shabbos and YO”T.