You may already be familiar with gem install, but if you add the -v flag, you can specify the version of the gem to install.

Using -v you can specify an exact version or use version comparators.

Install a specific version

gem install mypackage -v 1.0.0

Install a gem using version comparators

gem install mypackage -v '>= 1.0.0'

# or

gem install mypackage -v '~> 1.0.0'