Add a uibuilder node change the url to suit and deploy it. That creates a new folder on the Node-RED server, in ~/.node-red/uibuilder/<urlname> (assuming you have a standard installation and are not using projects).
That folder contains src and dist sub-folders and the src folder will contain the 3 index.{html,js,css) files plus some other things that you may not need. That is the source folder for all of your front-end code so you can put the templates into that folder or a sub-folder of it. Everything in that folder is available in your web pages.
It is quite likely that you will want to replace some of the standard index.html page with some of the template html but you will need to have a play.