If you have edit access to a page group, you can edit its settings by clicking the pen from the top right corner of the page.
From the i-tab 
you can set the basic information of the page and publish it. Only editors can see unpublished pages, so remember to publish all the pages you need!
From the pages tab you can manage the page group. You can change its name and description, share the page group, manage languages and archive the page group. You can't share single pages, you will always have to share the whole page group.
From the paintbrush you can change the page group's layout and styles.
From the bottom of the edit panel you can add more pages and change the page structure and save your changes.