I am looking about flocker how to on an atomic host, but I am not able to find anything.
Flocker isn't currently supported by either Atomic host. If you'd like to start a discussion about adding support I'd suggest sending an email to atomic-devel to start the dicussion.
The Fedora Atomic host will be adding more storage clients in the F24 release.
There is always the option to compose a local tree that adds the required packages for Flocker and rebase the official Atomic host image from the local tree.