How can you ensure that your users are aware of new features and improvements to your product?

There are various methods that can be used depending on your type of users. Can send the updates through email, pop-up, notifications, etc. Just make sure to have an active way of communication between you and your users.

I usually do this - Blast email updates and write blog posts for big updates - Notify users, show popup if its a webapp or send notifications if its an app

We announced it and explain it in our blog post and newsletter, we send notifications in the app too.