If you want to sell cryptocurrency - create an Order to sell cryptocurrency.
You can do it in the "Exchange" section.
Select a trading pair, then, under the trading table create an order to sell cryptocurrency:
- select "Sell"
- specify the amount of cryptocurrency;
- specify the price;
- click the "Place sell order".
Detailed instructions on how to create an order can be found here.
The order will be executed automatically, immediately after the buyer and seller's orders coincide.