By default, all pages* are restricted to be edited by an instructional role (TA or instructor). However, instructors can allow pages to be edited by students. 

*Pages can be refered to as Wiki Page, or Content Page as well

1. Click on Courses on the left hand navigation and then click on the name of your course. Click on pages link on the course navigation bar inside your course. 

Once you are inside pages area, click Edit in the upper right hand corner.

2. Enter your text on the document. Use the rich text editor to format your content. Be careful you don't accidentally delete someone else's text.

3. Click Save