I would say pretty easy, will you have a car? You need to head down to Lucca, then on to Pisa and continue south to Piombino. The drive should be about 2 hours and 15 minutes. Then you need to get on the ferry to cross to Portoferraio. There are ferries all day so you can just buy tickets for the next one when you get there or you can buy ahead by buying with either Toremar or Moby (they are owned by the same company so it's not like prices are competitive between the two, they tend to be the same). Fares are pretty standard during the summer, there is not much advantage to getting them ahead of time if you don't know your schedule and want to have flexibility of going there when you want.