I used your command in /elixir/apps/mishka_html/assets way and this is the result
/elixir/apps/mishka_html/assets # npm i ckeditor --prefix assets/
npm WARN deprecated ckeditor@4.12.1: We have renamed the @ckeditor package. New versions are available under the @ckeditor4 name.
npm WARN saveError ENOENT: no such file or directory, open '/elixir/apps/mishka_html/assets/assets/package.json'
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN enoent ENOENT: no such file or directory, open '/elixir/apps/mishka_html/assets/assets/package.json'
npm WARN assets No description
npm WARN assets No repository field.
npm WARN assets No README data
npm WARN assets No license field.
+ ckeditor@4.12.1
added 1 package from 1 contributor and audited 1 package in 8.348s
found 0 vulnerabilities
it shows me ckeditor@4.12.1, but my ckeditor version is 5 not 4 
and now how can I load it on my app.js file
