The easiest way to handle and manage gems is by using
bundler. Bundler is a package manager comparable to bower.
To use bundler you first need to install it.
gem install bundler
After you have bundler up and running all you need to do is add gems to your
Gemfile and run
in your terminal. This installs your newly added gems to your project. Should an issue arise, you would get a prompt in your terminal.
If you are interested in more details, I suggest you have a look at the docs.