Assets, based on their location, can be classified as:
source assets: the asset files are located together with PHP source code which cannot be directly accessed via Web. In order to use source assets in a page, they should be copied to a Web directory and turned into the so-called published assets. This process is called asset publishing which will be described in detail shortly.
published assets: the asset files are located in a Web directory and can thus be directly accessed via Web.
external assets: the asset files are located on a Web server that is different from the one hosting your Web application.
a: replace module_name with your module name like here my module name is backend
b: Rename the folder as you desire. Here I renamed it to template. Now my folder directory looks like backend/web/template/
3: Go to module_name/views/layouts/
a: Create files as per your choice like header.php, footer.php, menu.php, etc.php. Here we are going to create three files named header.php, side_bar.php, footer.php assuming that we have one file inside layouts folder named main.php. If not create one with the same name.
4: Go to module_name/web/template/ open index.html in one of your favourite text editor
a: copy the header part code as highlighted in screenshot, and past it to header.php
b: copy the header part code as highlighted in the screenshot, and past it to side_bar.php
c: copy the header part code as highlighted in screenshot, and past it to footer.php
5: Copy all content of index.html to main.php and remove those part which you already have copied and pasted it to respective files. For example remove header, side bar, footer content respectively. Now remove the main content part as highlighted below in screenshot.
6: Now prefix to css and js path this code to make the file path dynamic :