Constantly educate your users about the product.

Almost every product is too complicated to be adopted fully in the first day. But what you can do is educate your users a little every day about values that your product provides. This process is called ongoing onboarding.

Send your users messages showing more features of your product.
You can even do it more smartly and monitor what features the user already used, and send messages only about features that he does not use yet.