Step aggregates all liquidity pools across multiple protocols on Solana. The 'Opportunities' page gives an insight into a list of available pools and you can sort these pools by a number of metrics or search for a particular coin or pair you are looking for.
Click on 'Swap' on the left side bar to bring up the Swap and Liquidity tabs. On the Liquidity tab you will be able to select the pool you want to add liquidity to.
You must have a balance of both currencies to be able to add liquidity to a pool. To add liquidity press 'Add Liquidity' and approve the related transaction in your wallet. Your pool LP token should now be shown on the Step Dashboard in a few seconds, if not click the refresh button on the top right of the page.
To remove liquidity from a Step pool, navigate again to the Liquidity tab on the Swap page and you will see the LPs you currently own listed below, by clicking on one it will expand to show more information.
To remove liquidity click on 'Remove Liquidity' and you will be taken to the page below where you can select how much to remove from the pool.
When you have moved the slider to the amount of liquidity you want to remove, click 'Remove Liquidity' to execute the transaction to remove. You will then see a success notification and the coins will be back in your wallet.