Now to link your MetaMask account to Splinterlands you must create a MetaMask account. Im not going to cover how to create MetaMask account but there is plenty of guide's on how to do that.
How to Link:
1.Go to Splinterlands and click on your username and click on link external wallet
2. Then click on Binance Smart Chain
3.At this point open your MetaMask account and copy your address
4.Then paste your address in the address space
5.Then press i acknowledge... and then save and your done