How can I add a theme template to site? Bootstrap has templates like new age, creative, clean blog, etc. How do I add these templates to my site?

My workflow didn't work out well.


I copied the starter kit less to themes/custom
I renamed it to testtheme
I renamed all THEMENAME.yml files to testtheme.yml
I executed git clone https://github.com/BlackrockDigital/startbootstrap-new-age.git


Edit:
- Installed and set as Default (backend)

Unformatted bootstrap


edit 2:
global-styling:
 ` css:
    theme:
      css/style.css: {}
      css/new-age css: {}
      css/new-age.min css: {}

bootstrap-scripts:
  js:
    js/new-age.js: {}
    js/new-age.min.js: {}
Follow the following steps to add the bootstrap:

1. Put the bootstrap theme in the theme folder.
2. If you want to create a sub theme then copy the cdn folder from starterkits and rename. (themename)
3. Rename .info.yml , .libraries.yml and .theme files with your themename. 


Include the CSS in theme.libraries.yml file. Like below

global-styling:
 css:
  theme:
    css/style.css: {}

global-scripting:
 css:
  theme:
   js/script.js: {}