Long position means buy position. You can take a buy position and can square off on or before expiry.
For example: If you take a long position, you're going to be entering a stock futures contract to purchase shares. Your futures contract has a price of Rs. 5000 when you enter the contract. But if the price of ABCs stock rises to Rs. 52 per share in the coming month, you can sell your contract for Rs. 5200.