Here are the steps in order to enable SSL in Siteground hosting. Log in to your Siteground account and go to Security > SSL manager.
Select the website for which you want to enable SSL. Then choose the "Let's Encrypt" SSL and click on "Get".
A message will be shown that SSL has been installed for your website. Now click on the 3 dots and click on "Enforce HTTPS".
Click on the toggle "Enforce HTTPS" to enable HTTPS on your whole website.
After completion, a message will be shown that SSL is enabled on your website.