First, make sure you assign your testers on your Shop manager. To get in touch with all testers of a specific pattern head over to your shop and click the testing icon or use the settings icon and then select 'Manage testing.' A pop-up will appear. Select the 'Message testers' option and type in your message. Once you are ready, click the 'Submit' button. Your group message will be sent and can be found on your personal profile on the community tab under the 'Messages' section. You can also message approved testers directly from your Shop manager by clicking the 'Message Testers' button.