If the pool you wish to add liquidity to does not exist, you can create it. There are two important things you need to prepare: 1) A pair of tokens (A+B) that you wish to provide, and 2) 100 KSP tokens to pay for creating the liquidity pool.
You need to scroll down to the bottom of the page, and find the ‘Add Liquidity Pool’ button and click.
As the first liquidity provider, you have to select the ‘Token 1’ and type a contract address of the 'Token 2' in the red box with the initial exchange ratio. After then, click the ‘Create a pair’ button.
Please, remember creating a new pair requires 100KSP tokens in your wallet.
*In KLAYswap, the initial exchange ratio means price.