The Login Lightbox collection lets you create a login popup in any page or addon.
To create a standard login popup, install this collection and add the class "loginLightbox" to any element on the page. When anyone clicks the element, a popup is created with the site's default login box.
To add a class to an
To change the site's login box to any custom addon, go to settings >> preferences >> security tab and select the addon you would like to use.
The Login Lightbox includes a Login Form Sample addon to use as a guide to create a new custom login.
There is a how-to for creating a custom login here: