Navigating on the Ledger Nano S works by pressing either of the two buttons at the top of the device. Press both buttons at the same time to begin the configuration of the device.
The first thing your Nano S will ask you is if you want to set it up as new device. We will press the right button to confirm the action, if you ever want to restore your Nano S (more on this below!), you will have to select the left button and it will start the restoration process by asking for your recovery words.
The Nano S will then ask you to set up a pin. This is an important step, as you will have to enter it every time you want to access your Nano S. The minimum amount of numbers needed is 4, and the maximum is 8. You can always change this pin after you are done setting up your Nano S. After entering it will ask you to enter your pin once again, to confirm it is correct. It's worth stating that if you enter the wrong pin number 3 times in a row, it will automatically reset your Nano S.
Next, the Nano S will give you 24 random words that you will have to write down on the provided card in the box. These are the recovery words, also known as seed, that you will have to use when you want to restore your Nano S in case it fails or you accidentally reset the Nano S. Once you've written down all of the words it will ask you to confirm your recovery phrase, in order to make sure that you've written them down correctly.
Do not write down these recovery words on your computer, as it will be just as unsafe as using a normal private key. Always write it down physically using a pen, on a piece of paper only you have access to. Also do not take a photo of your piece of paper.
Now your Ledger Nano S is all set-up and ready to be used!
In order to make your Nano S work with MyDashWallet, we will need to enable browser support for the Dash app (make sure to install it first if you don't see it yet).
First of all, open up the Dash app by navigating to it, and pressing both buttons at the same time to open it. Then press the right button to select "Settings", after that press both buttons to open it up.
Select "Browser Support", press both buttons at the same time to open it op, press the right button to select "Yes", then press both buttons again to confirm.
Now we are done configuring the Nano S to work with MyDashWallet. You can press the right button to select "Back" and press both buttons at the same time to go back to the Dash app. If you do this once again you will go back to the main menu with all the apps.
It's time to access our Nano S using MyDashWallet.org, make sure your Ledger is unlocked and in the Dash app. Now simply click the "Ledger Hardware Wallet" button and you are immediately in (easy, isn't it?).
Now you can see how much Dash you have in total on the top right, spend it or use one of the other features of MyDashWallet. Every action still needs to be confirmed on your hardware device.
Below your amount you will see a long list of different Dash addresses used yet (latest fresh one with QR code that can be scanned or copied to get more Dash to your hardware wallet). Over time this list can get bigger, each of the addresses can be clicked to check the status in detail. All of these addresses are safely stored on your Nano S, and they all belong to you can are used when you sending Dash automatically by the Ledger.
Ledger made a clear and easy to follow guide on how to restore your Nano S here.