If you simply want to add your own logo, or change the colours of the admin UI then this can be achieved via the Control Panel itself – see the section in these docs about Branding.
How to use
UI customizations are made by placing your files in the
perch/addons/plugins/ui folder. Depending on your installation, this folder may or may not exist. You can create it if it’s not there.
This folder includes a special file
_config.inc file to add a link to your own files.
This really just provides a mechanism to hook your own files into the interface without needing to edit any core Perch files. This means that your changes won’t need to be re-done each time you update Perch. However, be sure to test your changes after updating Perch in case anything that affects you has changed.
(We appreciate that the end of the page is not the most super-ideal place to be adding new CSS files. If making big changes where this could be an issue, it may be better to look at implementing your code with an app instead.)