Which Metal P-Chain address to paste
Use the Add Delegator output from the Metal Blockchain explorer, not an unused Receive address. That is true for WebAuth and for Metal Wallet (wallet.metalblockchain.org) — each wallet has its own P-addresses. WebAuth and Metal Wallet get you to the explorer different ways. Watch the matching video on YouTube (new tab) — we do not host these:
Watch the WebAuth video on YouTube. Watch the Metal Wallet video on YouTube.