[Beginner] Does an erc20 token contract require special code in its contract to be listed on uniswapV3 and add liquidity?

Or can I just add liquidity from uniswap.org UI?

I see some examples with uniswap router code but online tutorials do not mention any code.

Also, if required, can a separate contract be deployed for an existing erc20 token, to include the uniswap code?