What did frederick the great mean when he said " in my kingdom, everyone can goto heaven in his own fashion"?

It meant that Frederick II had lenient tendencies towards the different religions. It didn’t matter to him which religion or deity your worship, or whatever doctrine you wish to practice. Maybe it be Judaism, Catholicism, Buddhism, Islam, Zen, Taoism, Zoroastrianism or any –ism of the matter. People are shaped by who they are and Frederick understood and tried to avert religious matters. This made it a less and unpopular issue and crisis in his era. He believed in the people and characterized them regardless of their faith. 

The answer is installation.