We use some question – e.g. “Do you want to understand?” Then the mind has some interest.
For example, you want to understand why the mind suffers? If you really want to know, then the mind becomes interested. When you ask the 'why, what and how’ questions, and the mind doesn’t know the answer, it then becomes interested.
Having interest means using wisdom energy. If you want to understand nature, then you become interested.
In the beginning, it is difficult to be interested because meditation objects are so neutral. The mind becomes interested only when it is exciting, but neutral object is only form, cold, touching – how to be interested in this kind of object? But if you try to be aware again and again, you become more familiar with these objects.
Like a game – in the beginning when we don’t know the game, we’re not interested; but when we play again and again and become more skillful, we then become interested.
When we know more about the subject, then more interest arises. That’s why you need to continue to practice a lot.