Our preferred way: reach the beautiful city of Nice, and let us take care of the transfer to Porquerolles (bus + ferry). Nice Côte d'Azur Airport is an international airport with excellent traffic connections, and, of course, there is a train station.
Reach the ferry terminal La Tour Fondue and then cross the sea. It is a good trip, but easier to prepare for locals. More information is available on the blog.
Porquerolles is beautiful and welcoming, but it is a small island: be prepared if you have specific needs. Ask to the organizer or contact the Porquerolles tourist office.