you have to do 14 weeks before 4th year starts during the holidays (which is when you have to hand in the report for Animal Husbandry)
its 4 weeks horses, 2 weeks dairy cattle, 2 weeks beef cattle, 2 weeks sheep, 1 week poultry, 1 week pigs, 2 weeks of whatever you want (vet clinics, wildlife, more farms, etc)
you organise it through uni, they have a database of all the places you can go to and you put in your preferences before holidays start (1st years get last preference though). but you can find places on your own that are not on the database and fill in a form and give to uni. if the farms are too far away (which they usually are), you can apply for travel consideration and get 1 or 2 days off depending on how far it is
you have a list of skills saying what you have to do eg. horses: pick up feet, saddle, pigs: dock tails, inject, poultry: measure respiration rate, etc...
you will get told all these things anyway and get heaps of other info, its lots of fun. at least you will have something to do over the holidays!