To supply to the LLP, you can deposit any one of the assets in the liquidity pool. Depending on the current weight of the asset in the pool, you may be able to deposit for lower fees, so double-check the assets list and the Fee in the Supply window.
Once your assets are deposited, your LLPs are automatically staked and earning yield for you.
To redeem your assets from the LLP, click on the 'Redeem' tab, input how many LLPs you want to redeem, and which assets you want to redeem in.
For a visual walkthrough, see the video below.