Click the button in the top-right corner of Nebulb (where the email associated with your license is shown) and the license management menu will appear:

Then you must press the option "Change password" and the following window will appear:

Then, just click the confirmation button and go to your email inbox and look for a new email from Nebulb. It will look like this:

Copy and paste the confirmation code and press the button:

Finally, enter your new password:

Click the confirmation button to update your Nebulb password.