The features you should look for in an anti virus software package would be, automatic scanning of E-mail attachments, downloads and web pages. The software should run in the background and load when the computer boots up. The software should provide you with updates and this update process should become a routine for you. The help file is the best place to look for learning about your scanning software. Go ahead and plan on upgrading the software every couple years.
Lets cover installing software briefly.
When you purchase software you are paying for the development of that software so generally speaking it should work. The best way to install software is to let it answer its own questions when installing. The default options that the software selects when installing itself is always the safest route. After you install any software learn it by playing with it, explore the text menus and see what is common with other programs and view the help file. You cant break it.