Step 1: Login to your cpanel and locate the Let's Encrypt icon. You can find the let's encrypt icon under the security section in the cpanel.

Step 2: Click on "ISSUE" at the right end of the listed domain you are installing for.

Step 3: After clicking on "ISSUE" in step 2 above, allow the page to process and provide you a details of the installation about to be done as shown in the screen shot below.

Step 4: Click on "ISSUE" in the screen. You should get a successful response as below:

Congratulagtions!!! You now have Let's Encrypt installed on your domain.