You can create dashboard widgets using a different data source account to the one you've already connected to Geckoboard.
Make sure that you are logged in to the correct data source account elsewhere in the browser or logged out completely.
Create a new widget for that data source, or edit an existing widget on your dashboard.
Click on the name of the existing connection being used to open a drop down menu. Click + Add connection.
If you widget configuration opened on a screen away from your dashboard, click the + Add button beside the Account
Follow the on-screen steps to connect your new account.