This may become a roadblock, in order to use vue, you will need to understand the concepts of html/css and javascript. There are many resources online, i learn a lot from traversy media on youtube, he has awesome tutorials about all those subjects, from simple to more advanced.
The best way to learn is by doing. Read through the examples, play with them by adding a few of your own bits and pieces to see how it all fits together.
There isn't a step-by-step guide for a very good reason. uibuilder itself is mostly a conduit for communicating between Node-RED as a server managing data flows and your front-end web code.
A basic uibuilder flow is 3 nodes long (see the examples) and the basic front-end code is a couple of dozen lines (see the "simple" example).
The skills lie in writing front-end code. uibuilder lets you use standard web development tools. So to learn, you should pick a simple web tutorial for VueJS and follow that.