1) Open Metamask, and select "Custom RPC" from the Network Dropdown.

2) In the "Custom RPC" Settings, add in the xDai network details and click Save:

• Network Name: xDai

• New RPC URL: https://rpc.xdaichain.com/​

• ChainID (Optional): 100

• Symbol: xDai

• Block Explorer URL: https://blockscout.com/poa/xdai​

Connecting to a Hardware Wallet

Instructions for using MetaMask with a Ledger or Trezor: https://metamask.zendesk.com/hc/en-us/articles/360020394612-How-to-connect-a-Trezor-or-Ledger-Hardware-Wallet​