To withdraw Flare tokens from the Kraken exchange you first need to login to your Kraken account.
Navigate to Funding in the header.
Press the Withdraw button on the Account balances row.
Search from the asset you want to transfer, this works for Flare, Songbird and many other assets.
If you haven't transfered to your Bifrost Wallet address before, you need to add your address for the token you want to transfer by pressing "Add new withdrawal address". After that, you select the amount you want to withdraw and then press the Withdraw button.
If you need to add a new address, you paste the address in your Bifrost Wallet into this window and add a description for future withdraws. Learn how to find your address.
The last step is to confirm the transaction, make sure that the address and amount is correct, and then press Continue.