If you want to send your BTS coins to another BTS wallet, you need to use 'Send' option in the main application menu. You need to know the destination BTS wallet name 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 BTS to BTC transaction. Also, while sending coins you need to remember about transaction fees. This fee goes to reward miners and support the BitShares network itself.