You can leave the Vendor Organization you have joined at any point.
First, log into the Euna Supplier Hub: https://vendor.bonfirehub.com/
Click the Account Settings tab at the top, then My Team on the left navigation bar. You'll see a list of any/all users who are also members of the same Vendor Organization. To leave the Vendor Organization, click Actions > Leave Organization.
You'll be presented with a confirmation popup. Click on your desired choice to move forward.
You can choose to stay in the organization, resulting in no changes to your account, or you can choose to leave the organization. If you select Leave Organization, the page will refresh. You will no longer be a part of that vendor organization, and you'll be prompted to create your own: