Once you have arrived at uniswaps home page(https://app.uniswap.org) hit pools towards the bottom of your screen.
Hit the new positions to create your liquidity pool position.
On select token button it will pull up a list and you will select ButtCoin
You can select the fee tier(although you should just choose 0.3%) as that’s the most common. You can also dictate price range, but I just maxed my range out by hitting full range below. Also below you will select how much matic and buttcoin to add.
Then you hit add and sign transactions and you are done!