Mechanism of trading in future contract?

Basically, you buy (go Long) on a futures contract when you think the underlying asset is going to go up and you go short on a futures contract when you think the underlying asset is going to go down.

When you go long or short on a futures contract, you only need to pay a small deposit (typically about 10% of the price of the underlying asset) known as the "Initial Margin".

Winnings are added to your margin daily and losses taken from it. When your margin drops to a level known as a "Maintenance Margin" due to losses, you will receive a "Margin Call" to top up your account back to the initial margin level.

You can close off (offset) your futures position at anytime in order to cut loss or take profit.

For more details on how futures trading works, please refer to the link below.