Installation is terribly simple - it’s a gem, after all. You can either install it manually

gem ama-entity-mapper

or leave it up do Bundler:

echo "gem 'ama-entity-mapper'" >> Gemfile
bundle install

All what’s left is to require the gem in code and start using it:

require 'ama-entity-mapper'

# ...

value = AMA::Entity::Mapper.map(input, type)