Create a wallet with Shamir Backup

• You will be presented with sequences of random 20 or 33 English words, each displayed on the screen of your device. These words will never be shown on your computer screen. Do not use backups offered to you by your computer.
• The word-sequences are referred to as "recovery shares". If used correctly, the recovery shares can later be used to recover a wallet in case of theft, loss, or destruction of the Trezor device.
• Keep the recovery shares written offline. Do not take pictures of your recovery shares, do not make digital copies of your recovery shares, and never upload them online.
• Use paper or other suitable platforms to keep your recovery shares offline. 

Creating a new wallet with Shamir backup

• Start up Trezor Suite and connect your Trezor Model T
• Following the initial "Firmware" (check / installation) step, in the "Wallet" window choose 'Create new wallet':

• Then choose 'Shamir share backup':

• You'll then need to confirm this action using your Trezor Model T:

• Then click on Create backup in Trezor Suite:

• In the next window, read and confirm that you've understood the instructions by clicking the three boxes, then select Begin backup:

• To proceed with setting the number of recovery shares, press Continue on your Trezor Model T:

• Set the number of recovery shares by using the plus (+) and minus (-) buttons on your Trezor Model T. Once you are happy with your choice, press Continue:

• You Trezor Model T will then display confirmation that you've set the desired number of shares:

• Press Continue to proceed with setting the threshold, again using the plus (+) and minus (-) signs to change the value:

• Once you've set the threshold value, press Continue. Your Trezor Model T will then display confirmation that the threshold value has been set:

• Press Continue and proceed with writing down all of the recovery shares. Before your Trezor Model T displays the word lists, you must confirm that you understand you should never make a digital copy of your recovery shares:

• Your Trezor Model T will then display the words comprising your recovery shares. Please record these with the correct spellings and in the correct order:

• Once you have made an offline copy of your recovery shares, your Trezor Model T will show confirmation that the backup process was successful:

For more information explaining Shamir backup and how to use it on the Trezor Model T, you can read the article What is Shamir backup? and check out the following video: