Your first port of call can always be the Home screen. From here you can navigate to any area of Football Manager Mobile™ 2020; simply select the Home icon on the sidebar from most devices.
The screen is divided into a series of panels. You can navigate to all things to do with the club you are managing, to your managerial hub or to the wider footballing world and its competitions. You can run a search for a player or a club, or configure your game options.
You can always access your Inbox from the uppermost panel spanning the width of the pop-up overlay, or on the side menu on select devices. If there are unread items, it will inform you of how many there are, otherwise it will read 'No New Messages'.