If you want to send your BTG coins to another BTG wallet, you need to use "Send" option in the main application menu. You need to know the destination BTG wallet address for this purpose. Do not forget that inside light wallet application you can make only one currency direct transactions, for example, you are not able to make straight BTG to BTC transaction. Also, while sending coins you need to remember about transaction fees. This fee goes to reward miners and support the Bitcoin Gold network itself.