Importing or Creating Private Keys

Import Existing

If you already have a BIP-39 based wallet, or other private key material, you can import this directly into the Coldcard at setup time. Choose Import Existing from the main menu.

main menu import existing

From the import menu, you can import seed words generated on another system, restore a backup file, import a raw XPRV or roll a dice to make your own value.

import menu

24 Words
18 words
12 Words
Choose the number of words: 24, 18 or 12 words and the following menus will allow you to drill down to appropriate BIP-39 word (English only). The final word is a checksum value that verifies the other words. The Coldcard will calculate the 8 possible final words after 23 are provided.
Restore Backup
Import a backup file from another Coldcard. You will need the backup file (7z) on the MicroSD card, and you must enter a 12-word password that was provided at the time the backup was created.
Clone Coldcard
Starts the secure cloning process. You will need a MicroSD card. Insert it and a small file is written to it. While keeping the power active to this Coldcard, take that card to the source Coldcard from which you want to copy. Go to "Advanced > Backups > Clone Coldcard" and a special encrypted file is written to the card. Bring it back to the (still powered) blank Coldcard and press OK. The data is restored and the Coldcard reboots. Everything except PIN code will be duplicated from the other Coldcard. Both Coldcards must be running v4.0.0 or higher firmware, and should probably be same version exactly.
Import XPRV
To import an XPRV, you must provide a cleartext file on MicroSD with a BIP-32 base58-serialized extended master private key. It should start with xprv and be on a single line of a text file. The rest of the file is ignored. Please note there is no encryption for this method, and therefore, it is very hazardous and only recommended for testing purposes.
Dice Rolls
You have the option of creating a unique seed value by rolling a six-sided dice (D6). Just keep pressing 1–6 as you roll. At least 99 rolls are required for 256-bit security, and if you operate with fewer rolls, you will be warned. Press OK when complete, and the equivalent seed words are shown so you can write those down instead of the dice numbers. As usual, the word quiz is conducted before the seed is saved. Learn how to completely verify the dice rolls using Tails

The final item in the menu is a bit different because it allows you to create the private key directly. In that way it's not really an 'key import', but a 'create key'.

Mix-in Dice Rolls

This is not the only way to introduce entropy from dice rolls. Any time the Coldcard is showing the seed words on-screen, you may press 4 to "mix in" additional dice rolls. In this case, since the entropy of the Coldcard is being used as a starting point, it is safe to add as few or as many rolls as desired.