Login to the backend admin panel of your website
1) Select Site >> User Manager
1) In the User Manager, click New to add a New User
1) Fill in the new users details
2) Select to make this User an Author
In the same new User panel, give the new user access to Editing tools and select your language options
Save these new User details
You will now need to visit the Article Manager found under the content tab.
Either create a new Article or select the Article that you wish to become the new Users page.
Open this Article
Under Article Parameters, change the name of the Author to that of the new User you have just created.
The new user can login to the front end of the website, but the editing option will only appear on the page or pages that they are the Author of.