When signing up for Backblaze, beneath the sign-up button is the region selector.
From the free trial page the selector is here:
From the B2 sign-up page the selector is here:
From the group page the selector is here:
Click the down arrow next to "Region" and select the region you would like the account to be in.
Please note: There is not a way to transfer data from one region to another. An account will need to be created in the new region and the data will have to be re-uploaded to this new account.
You can manage multiple accounts in different regions by placing those accounts inside of a unified Group. To learn more about creating a Group, please visit the Creating a Group FAQ.