Adjusting margin on an open position means adding USDC to or pulling USDC out of the collateral allocated to a position you already have running. You are not closing or reopening anything. You are changing how much of your perps cash balance is sitting behind the position right now, which shifts how much room the position has before it gets liquidated.
To do it, open the position and tap the pencil icon. From there you will see options to add or remove margin. Pick the direction, enter the amount, and confirm. The position updates with the new collateral.
Adding margin pulls more USDC from your available perps cash balance into the position. That gives the position more cushion. Your effective leverage on the position drops, and your liquidation price moves further from the current market price. Effective leverage is the leverage your position is actually carrying at any given moment. It starts equal to whatever leverage you selected when you opened the position, and it shifts as the market moves or as you add or remove margin. Adding collateral is one of the cleanest ways to give a position more breathing room without closing it.
Removing margin pulls USDC out of the position back to your available perps cash balance. That frees those funds for other trades, but it also raises your effective leverage on the position and moves your liquidation price closer to the current market price. The position becomes thinner. A smaller move against you is now enough to liquidate it. Only do this when you are comfortable with the higher risk on the remaining position.
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