You may close your current position via 2 methods:
1. Close your current position by clicking on the "Limit" or ”Market" icons and follow through on the request.
2. You may place a new order in the opposite direction of your current position (eg. current position 100 BTC/ETH Long, to close the position, place an order for 100 BTC/ETH Short). The position will be closed once the order has gone through.