I was wondering where the Halachot about sleeve length for women come from and what exactly they are (or where i can find them). Thank you.

Shalom U'Vracha The Mishnah (Ketubot 7:6) speaks about the proper way for Jewish women to behave (Dat Yehudit) and explains that she should cover her arm (See Gemara Ketubot 72b Rambam Ishut 24:12 and Shulchan Aruch Even HaEzer 115:4) The exact definition of arm the Mishnah Berurah (75:2) holds that the entire arm should be covered. The Mishnah (Ohalot 1:8) defines arm as the bone from the elbow to the hand, therefore there are opinions that the sleeve needs to cover the elbow but does not need to reach the hand. (See Mishnah Berurah ibid.) Kol Tuv