You can create your own Custom web pages in the Content > Site Page Structure page.  After you have created a Custom page, to edit the page, go to Content > Page Edit.  The Page Edit page lets you edit the content area of the different pages available on to your organization. 

1. Click on the drop down arrow to select the page you want to edit. 
2. The currently saved content will display in the Edit Page Content area on this page. 
3. Modify the content using the tool bar that is available -- like you would edit a page in MS Word.   
4. Click Save when you are done.