How to add a subdomain in Plesk This demo assumes youve already logged in to Plesk. Now lets learn how to add a subdomain. Click the Add Subdomain button. Enter the subdomain name you want to create. The document root folder is automatically created, which you can rename if you wish. Click OK when ready. This is the end of the tutorial. You now know how to add a subdomain in Plesk. Thats it! The new subdomain has been created, and you can manage it from here.