Written By…

My blog, https://www.laatedaa.com is not showing the Written By, NAME. I recently have another author writing posts for me and I would like his name to be shown next to the date and Title, such as Written By, Andrew on 3/03/03. How would I go about doing this? Is it possibly my template I am using? Is there a plugin or script that I can add it to get this functionality? Thanks.