There is probably nothing more powerful to make people use your product than triggers. Triggers remind them about your product, remind them why they should use it. And there are many types of triggers at your disposal, for example, emails, push notifications, and advertisements.
The bad way of using triggers: begging users to do something.
The good way of using triggers: using one of these six principles of persuasion that Robert Cialdini presented in his book Influence: