Use myetherwallet add custom token info for SONM then you will be able to send them the exchange address. Do remember you also need to have some ETH on your address to perform transactions.
Thanks a lot, I'm googling to find out custom token info for SONM. SONM is my first try, I also tried to buy Status ICO but wasn't able to buy status SNT. Too many people buying SNT, but no topic talking about SNT here ; so werid