Leveraged long orders bet on the rise of an asset's price, and it amplifies the returns (and losses). For instance, if you made a leveraged long order with 2x leverage, and the price of the underlying asset rose by 10%, your return would be 20%.
Leveraged long orders are made by taking out loans denominated in a stable currency (like DAI and USDC), with the collateral denominated in the asset you want to long. The loaned stable currency is immediately converted to the asset you want to long. This means that you would be exposed to the asset's price changes not only through the collateral, but also through the loaned assets, effectively amplifying your returns (and losses).
Click "Make Investments" on the manager portal's header, select an asset with the label "Margin Trading", and you will be able to select the leveraged long order option, with up to 4x leverage.