A module adds a feature to Jamroom. Blog, Audio, Forum, Comments, Search, Site Builder and the Marketplace are all modules. Install the ones your site needs from the Marketplace. Installing modules you don't use only adds settings to look after.
Each installed module has its own entry in the ACP, under one of the categories in ACP > Modules (see The Admin Control Panel). Use the Search box above the categories if you can't find one.
Most modules are set up in two places:
To see the Quota Config settings of every quota side by side, use ACP > Modules > Profiles > Profiles > Tools > Quota Compare.