You can add sales representatives by clicking the 'new sales rep' icon at the top right corner of the screen. This will redirect you to a page where you can input data of a new sales rep.
Click save once all the fields have been inputted and you should be able to view your new sales rep.
To edit a sales rep, simply click on the desired sales rep, a small window will pop up and the options of deleting or editing selected sales rep should appear. Click on the 'edit' icon and make all the necessary changes to the sales rep. Once completed, hit save and your changes to the sales rep should now be updated.