Click on the "Add Liquidity" button
Select the token pair you wish to add liquidity to by using the drop down menus labeled "Select token". Tokens can be selected in any order. Filling in the amount of one token will automatically fill in the other with an equally valued portion.
The Add Liquidity Interface
When ready, click on the "Supply" button
Make sure you sign the transaction in your wallet
Your liquidity has been added
Click on the pair you wish to manage
Click the "Remove" button
On the Remove Liquidity page, you can select a quick percentage button or fill in your own.
Click approve when ready. You may have to sign for this transaction if it's the first time you've managed LP tokens for this pair
Click the "Withdraw" button
Last step: Sign for the transaction in your wallet