OpenStack clouds
Although Juju doesn't have baked-in knowledge of your OpenStack cloud, it does know how such clouds work in general. We just need to provide some information to add it to the list of known clouds.
Adding an OpenStack Cloud
Using the Juju add-cloud command, it is easy to add your OpenStack clouds to
Juju's list of known clouds. The command is interactive, and will ask for
a name,endpoint,authorisation method(s) and regions to use. (If you are unsure
about endpoints and regions, they will be listed in the .novarc file, if you
have one for your OpenStack.) A sample session is shown below.
Running...
juju add-cloud
...will enter the interactive mode. Enter the desired values to continue.
Cloud Types
maas
manual
openstack
vsphere
Select cloud type: openstack
Enter a name for your openstack cloud: devstack
Enter the API endpoint url for the cloud: https://openstack.example.com:35574/v3.0/
Auth Types
access-key
userpass
Select one or more auth types separated by commas: access-key,userpass
Enter region name: dev1
Enter the API endpoint url for the region: https://openstack-dev.example.com:35574/v3.0/
Enter another region? (Y/n): n
Cloud "devstack" successfully added
You may bootstrap with 'juju bootstrap homestack'
Note that it is possible to choose more than one authorisation method - just separate the values with commas.
Once the cloud has been added, it will appear on the list of known clouds
output by the juju clouds command. Note that the cloud name will be
highlighted to indicate that it is a locally added cloud.

It is also possible to define OpenStack clouds in a YAML formatted configuration file and register them with Juju. Please see the documentation for manually adding Openstack clouds for details.
Adding credentials
If you source a novarc file for OpenStack, or use the default environmental variables for accessing this cloud, you can simply get Juju to scan for the credentials and add them.
Run the command...
juju autoload-credentials
Juju will search known locations, including environment variables, for credential information and present you with a set of choices for storing them. Simply follow the prompts.
For other methods of adding credentials, please see the specific credentials documentation.
Images and private clouds
The above steps are all you need to use most OpenStack clouds which are configured for general use. If this is your own cloud, you will also need to additionally provide stream information so that the cloud can fetch the relevant images for Juju to use. This is covered in the section on private clouds.