This feature is only work for those who are having .blogspot.com sub domain. Those who are having custom domain they are not getting this feature. They have to buy that HTTPS certification form their hosting company. It will cost those who are using custom domain on blogger.
Before that you must have to know about HTTPs,
Hyper Text Transfer Protocol Secure (HTTPS) is the secure version of HTTP, the protocol over which data is sent between your browser and the website that you are connected to. The 'S' at the end of HTTPS stands for 'Secure'. It means all communications between your browser and the website are encrypted.After that blogger says
Turning on HTTPS Availability will allow visitors to view your blog over an encrypted connection by visiting https://mero-des-nepal.blogspot.com. Currently, this feature is only supported for Blogspot domain blogs.Previously you are getting only
https://mero-des-nepal.blogspot.comThis is very good feature that will help to make your blog secure and also help you to establish secure connection. It means all the connections and communication can be done in encrypted form.
To enable HTTPs feature on blogger blogs you have to follow below steps,
Go to bloggers dashboard and now just click on settings tab below that tab you will get new section HTTPS setting.
Their you will find yes/no button. To enable the setting you have to use Yes and if you want to turn off HTTPS you can go do dashboard and anytime you can switch yes to no.
Now what will happen to custom domain blogs,
Sadly yes you are not getting this feature for custom domain blog because you are using custom domain you have to pay for that to your hosting company than only you can able to use HTTPs services.