Cant connect metemask to uniswap..need some advice please!

Hi
I am trying to buy leash using uniswap. i have a metamask wallet and i use binance. i transferred some bnb from binance to the smart chain network i set up on metamask but uniswap cannot appear to connect to smart chain network/account on metamask. if i connect uniswap to the ethereum network there is no problem but my funds are in the smart chain/bnb network on metamask. i can connect pancake to the bnb network but you cannot buy leash there.
i may be using the wrong terms as im very new but if anyone is kind enough to respond it would be hugely appreciated. is there a way to transfer the bnb from the smartchain network i set up to the ethereum network?

thanks all

matt