Minting is purchasing a 'new' NFD, one that has not previously been created.
How to Mint an NFD
On the 'Mint' tab, search for anything you'd like. The NFD must be an alphanumeric containing letters A-Z and/or numbers 0-9, no special characters.
You are able to mint using a Ledger device. Make sure you're updated to the latest firmware as well as the latest Algorand Ledger app. You may also need to update your Ledger Live app.