We've just installed a ceiling fan.

Everything appears level, except that the post is crooked.

Any ideas on how to rememdy this?

Hi there.........
when you say post I assume you have a fan that is being suspended by a down rod ....
If this so, maybe the rod is crossthreaded in where the rod threads into the ceiling fan.
Other then that I suggest you return the rod for another one.
Christopher
CHOLE4ELECTRIC@aol.com