You have to apply to referee at one of their tournaments. You can travel as an independent but you tend to get more and better games if you're part of a party from a recognised organisation, such as a Referees Association or County FA.
Either way, you need international clearance to referee outside of England.
As for experience, you will probably gain much from working with a team of three in almost every game and from the feedback provided by the observers. It can accelerate your development and make a massive difference to your profile and ability on your return home. It can however also be a little daunting if you do not have any previous experience of tournament refereeing, especially the politics, organisation, communication of appointments which can be late, games over run, meaning mealtime are missed, then there's the temptation of being sucked into the party approach adopted by some attendees, who treat the "tour" as their summer holiday rather than a development opportunity.
Some of their tournaments are already full for next summer, so if you're going to go, apply soon. If you know anyone who had travelled to one before, you may want them to put in a good word for you so you get accepted.
