rails consoleを起動して。

接続設定

ddb = Aws::DynamoDB::Client.new(
    endpoint: 'http://localhost:8000', 
    region: 'ap-northeast-1'
)

=>
#<Aws::DynamoDB::Client>

テーブル名確認

result = ddb.list_tables
result.table_names

=>
["TestTables1", "TestTables2"]

値の確認

result = ddb.scan(
    table_name: 'table_name'
)

result.items.each do |item|
  puts "-------------"
  item.each do |key, value|
    puts "#{key}: #{value}"
  end
end

=>
[{"key1"=>"value1",
   "key2"=>"value2",
   "key3"=>"value3"}]

AWS SDK for Ruby v2 で DynamoDBを使う - Qiita