Dear Rabbi We have 2 types of fasts. One is major [Sunset to Nightfall on the next day], and one is minor [Dawn to Nightfall]. I wonder if I am obligated to read any particular passage or do anything else prior to getting any types of fast. Whether the ones that are in the calendar like the upcoming one, Asara be Tevet, or if I want to do it as a personal Teshuva on a random day. I can't thank you enough for your time.

For the official public fasts, there is no need to "accept" them, for they have been accepted by the nation of Israel. But regarding private or personal fasts, one accepts them officially during the afternoon mincha prayer the day before, and then the fast begins the following morning.