I assume you're working on Gnome 3 desktop.
1. I don't know how to do that. Probably you could've left empty boxes while installing your system. I'll look for easy solution, but won't promise anything
2. When you view applications installed on your system (Activities -> Applications) you can right-click on application and add it to favorites. It will show on applications panel on left when clicking Activities next time. Right-clicking on existing apps in that dock will give you option to remove them. Btw you don't have to click on Activities, you may simply move your mouse to the top left corner or press windows button on the keyboard.
3. There's program called gnome-tweak-tools in which you can change the size and type of fonts. While you're at it you can check other options in there - some are useful
4. Click on your name in top-right corner and press Alt - you will see the option to power down your machine.
There are few official and some unofficial extensions for gnome shell. One adds normal applications menu next to Activities button, another changes the default actions in top-right menu (so you don't have to press alt every time you want to quickly shut down). If you decide to install those extensions you can control them through gnome-tweak-tool and dconf-editor