Update early 2019: Please make sure to set 'Public keys exports approval' to 'Auto approval' in your Dash app Settings on the Ledger Hardware device to avoid timeout error 5 when you have multiple used addresses already.
Enabling your Ledger Nano S to work with MyDashWallet
Using the Ledger Nano S with MyDashWallet
Restoring your Nano S
Ledger made a clear and easy to follow guide on how to restore your Nano S here.