Since we are already here or in this situation, we should accept it, stay calm, and make the best of it.

既然已经来到了这个偏僻的小镇，我们就既来之，则安之，先找个地方住下吧。

Since they have come, we should make them comfortable or help them settle down (the original Confucian meaning regarding subjects or guests).

既然招揽了这些移民，就应既来之，则安之，让他们在这里安居乐业。