1) Start on the Trade page and select the market of your choice from the dropdown (EUR/USD or ETH/USD). On the right hand side you will see a panel to open a Long or Short position. You can either enter a number in the input boxes or you can drag the leverage slider to specify the notional size of your position.
If you expect the price to rise, you should select Long and if you expect the price to fall, you should select Short.
The minimum position size is 35 USD.
You can use what is available in buying power. However, note that the maximum buying power is your collateral balance multiplied by max leverage. The higher leverage you use, the higher risk of liquidation.
2) Once you're satisfied with the input amount, click on "Open position" and confirm the transaction from your wallet. Wait for the interface to update and you will see your position show up in the lower panel of the screen.
5) Congratulations! You have now successfully opened a position, and you can now monitor it for profit and loss 🎉