Importing html and css in vaadin+ SpringBoot Project

In my new project i want to add html and css in my springboot project with vaadin. is there have any tutorial or documentation for learning?
Thanks in advance

Which Vaadin version are you using?

now i am working with vaadin 8.4.4 but i want to shift in 10

The approaches are quite different between 8 and 10, and it also depends on what exactly you are doing. For Vaadin 8, maybe you could look at the docs about CustomLayouts: https://vaadin.com/docs/v8/framework/layout/layout-customlayout.html and Themes: https://vaadin.com/docs/v8/framework/themes/themes-overview.html
whereas with Vaadin 10+, maybe the Template API: https://vaadin.com/docs/v11/flow/polymer-templates/tutorial-template-basic.html and Theming Flow Applications: https://vaadin.com/docs/v11/flow/theme/theming-overview.html

i will let you know after studying this.Tnx