Activate portal in Openemr, then link to <your_openEMR_URL>/portal
For example, if you have a wordpress website with menu items, just add custom menu item linking to URL.
Making it work though… I’ve had many issues with it especially with patient registration and still working on it being able to deliver a basic patient self registration process. Used to have issues with registration forms not being delivered to OpenEMR backend but now can’t even get it past email verification step.