Go to Admin view and click on Pages tab from the top menu.
Click on the pen icon under Edit/View of the page that you want to modify.
If you want to modify the content of the page, click on Open Visual Builder and move items around or add new ones.
If you wish to change who has access or for whom you restrict the access of the change, go to Permissions tab and add the groups that you wish or change the settings of the existing ones.
If you wish to change the settings of the page, go to the Settings tab. From here you can change the name of the Page, how it is displayed, if you want it to be visible to the sidebar and with what image.
From the Revision History tab you can track all changes that were made on this page and by whom. By clicking Replace Content you can go back to the page at the state that it was at that time of editing.