The first day of Selichos is a very special day in Belz. The Belzer Ruv z”l used to say that every Kehilla has their special day outside of Rosh Hashanah and Yom Kippur. In Chernobyl it is Erev Rosh Chodesh Elul, in Tzanz it is Shelosh Esrei Middos (a day before Erev Yom Kippur), and in Belz it is the first day of Selichos.
Selichos is said very early morning, followed by Shachris. The Rebbe Shlit”a is the Ba’al Tefillah and Chasidim come from all over Eretz Yisroel and beyond to the great Shul in Yerushalayim. After Davening, the whole Tehilim is said.
See here clips from previous years
Acquire Great Zechusim before Rosh Hashanah: