Click on the question mark icon on the top right corner and then choose Help & Support. You will need to fill in a form. Please add as many details as possible about the issue/question you have and if necessary attach any relevant files. Click the "Submit Case" button when you're done.
If you are logged in SDL Trados Studio to your SDL Language Cloud account, you can click on the connection icon in the top right corner (the one that says your name) of the main window then choose Manage Account. You will be redirected to the same website as the one mentioned above.