Yosef Karo, Translation:Shulchan Aruch — Orach Chaim 581…
“ We rise at dawn to say Selichot on the Sunday before Rosh Hashanah. If Rosh Hashanah falls on Monday or Tuesday, we start on the Sunday of the previous week (Minhagim) . A mourner is forbidden to leave his house to go to synagogue to hear Selichot, except for on the day before Rosh Hashanah when we say many Selichot. On that day, the mourner can go to synagogue (Piskei Mahar"i chapter 133) . It is important to search for a prayer leader for Selichot and the Days of Awe who is most fit, one who is learned and does good deeds. He should be at least thirty and married. ”
