Go to Aweber and sign up for the free membership Anurag. They have instructions on the site and they have a chat box if you need extra help.

You need an auto responder. Aweber is a great one

You should have a paid autoresponder such as AWeber or ConverKit, MailChimp, GetResponse, etc. Then once you have built an opt in form in your autoresponder dashboard, you can then install and activate the plugin. For example, Jay our Live training coach has AWeber and he activates AWeber plugin to paste the code for the opt in form to show on his website.

Check out Jay's training in Email Marketing last month if you haven't already. You can find the training by clicking the Live Events tab and watch the recorded training.

All the best,
Ferra