Step by step:
1) To add margin to your account to use Leverage, hit the green [Margin] button in the top right of your screen
Note: Sunflower Corporation provide an 'Isolated Margin', so before transferring any funds from your Derivatives account please select a required pair for adding the margin — for example, ETH/USDT.
2) The 'Amount' window will allow you to enter the desired transfer sum, while the 'Leverage' will indicate what size of leverage will be possible to use while making a trade. After you have checked everything, hit the [Transfer] button to proceed.
You can also use a video guide on YouTube