This theme will be added like a dependency repo to original project.
On your root (www-spin) of Hugo execute:
$ git submodule add https://github.com/matcornic/hugo-theme-learn.git themes/hugo-theme-learn
Next initialize submodule for parent git repo:
$ git submodule init
$ git submodule update
Now you are ready to add content and customize looks. Do not change any file inside theme directory.
Refer to this theme in config.toml.
