Apply on their sites, or in the shops i think you do it under "Volunteer" before you get a paid job with them =D.

You won't get a job in the offices etc where they get the most money from donations, so i don't know why you want to do it. Most people who volunteer are the type of people you see protesting about nearly everything they can protest against. Enjoy wasting time.

No such thing.

So I know there is all these charities and campaigns like greenpeace and campaign4consent and like you can donate money to them. But I want to work for them. I want to be setting up the marches and protests and giving speeches. How do I go about doing this?