you have to search in internet once and choose 3 best sites for  keeping coins. i  have to suggest  coinbase crypto site in this site it is one of the most rock solid bit coin exchange site. here we have to exchange easily more secure this site. second one is bitstamp. it is world largest big bit coin exchange site. next ploniex is one of the best site for  secure exchange purpose. so you have to choose these 3 sites for crypto currency.