There are three ways to buy/sell cryptocurrency on CEX.IO:

There are three ways to buy/sell cryptocurrency on CEX.IO:

Buy/sell in a few clicks  (for BTC and ETH)https://cex.io/trade/buysell/buy/usd
You may create a buy/sell trade order, it will take some time to be completed, but the fee is 0.2% at the most.https://cex.io/trade
You may create an instant buy/sell order, in case you are willing to spend/sell the exact amount. The fee is also 0.2% (please make sure that your balance includes both amount you wish to spend and fee).https://cex.io/trade

Thank you