Installing Spina is _reasonably_ straightforward, but there are some nuances (like routing) that you'll need to understand.
Installing Spina is a matter of adding a gem and then running a few commands:
bundle add spina
rails active\_storage:install
rails spina:install
You'll see a load of files being installed, most of which are migrations. At the very end you'll get a few prompts to name your app, add your email, and finally a password.
Note: If you get an error running spina::install, be sure to specify the version in your Gemfile, for instance
gem "spina", "~> 2.18