Within your DNN site, each module has a menu for MODULE SETTINGS.  You access the module settings by going into edit mode and then on the module, hover over the gear wheel of the module and click on settings. Learn more about the different settings and what you do with them.

In order to edit existing content, you need to have editing access to the site.  That will either be an Administrator role or a specific content editor type role.  If you need editing access, you will have to reach out to your site's manager. Step 1 - Login Step 2 - Navigate to the page you want to edit, then click on the edit pencil icon in the lower left corner

How do you add new content to a page?  DNN has two methods depending on if you are creating something from scratch or if you have a pattern that you want to mimic.   From scratch - you would choose the "ADD NEW MODULE" option Mimic a pattern - pick "ADD EXISTING MODULE" Here are the steps to do both.