Below, is a copy of the Bruny Island Ferry timetable published by the company themselves.  A map of the location of the ferry is below this timetable and is from Google maps.  Basically, to get to the ferry from Hobart, head south on the A6 to Kingston, then the B68 to Kettering and follow the ferry signs.   It takes about 35 to 40 minutes to travel to the ferry from Hobart.  The ferry is non bookable and so it is advisable to get in the ferry que early and you pay for the crossing as you drive on.  If you are arriving for the ferry by public transport, then be aware that there are no busses and only pre arranged tours.  One idea is though that there is a cycle hire close to the ferry terminal, again be aware that some of the roads are dirt track and dusty.  Let all the ferry traffic go before cycling on the roads.