You'll need some bones, any type, and the same number of pots and buckets. You'll get 5 tokens per set of those, so with 10 bones, pots and buckets, you'll get 50 tokens. You'll also need to have finished the Priest in Peril quest.
Go to the North-East corner of Morytania. Here you'll find a city, called port phatasmys, and a strange glowing thing called the "Ectofunctus".
There's a trapdoor near the Ectofunctus. Climb down it, and make your way to the bottom of this area. Here, you'll find some ectoplasm. Use your one of your buckets on the pool to start filling them up.
When you've done this, go back up, and climb the nearby stairs. Here you'll find a bone grinder. Use some of your bones on it to fill your pots with them. Once you have the pots of bonemeal and buckets of ectoplasm, worship the ectofunctus by clicking it.
For every pair of buckets and pots you use, you can right-click a ghost disciple and collect your ecto-tokens.