I realize that people some times have trouble with all the terminology in Drupal, but you really need to try; it is essential to asking a question that can be answered.

Modules provide code to make Drupal do things; they do not "show up" anywhere (other than a list of their names that you've already found). A module typically produces some kind of dynamic content that does display. Many modules produce this content in "blocks" - those boxes that are placed in one of the non-main content areas (left/right "sidebars", "header", or "footer").

Many modules also produce output in the main content area; you cannot move that. You can, however, add other modules that change the way it is formatted, such as the panels module that allows the main content area to be divided into smaller pieces ("panels").

Almost all modules come with either a README.txt or INSTALL.txt (or both) that give you more information on how to configure them. If they don't you can also check the handbook section for core< or contributed< modules.