The ManyCam watermark will be removed automatically once you activate the subscription. Please refer to this guide to do so.
If this doesn’t happen, please make sure you are running the latest version of the software and check that your subscription is enabled in ManyCam Settings > Subscriptions.
If the watermark is still displayed, please make sure to install the latest ManyCam update and check once again that your subscription is enabled in ManyCam Settings > Subscriptions.