It depends on the meaning of the verb because it can either mean 'to be focused on' or 'a formal marriage proposal'. In the 'to be focused on' form of engage, you say that you are engaged with or in something, or I will engage in ___. To be engaged with someone is to have a formal marriage proposal. For example "Maria and I are engaged."Or I was engaged to Thomas."

To 'engage in something' means to participate in, to be involved in, or to take part in. You can also 'engage someone in' something, meaning you are making them participate in something. To engage someone as [insert profession here] means to employ or to hire someone, though this is not a very common use. It can also refer to a machine or engine of some sort, as in 'engage the thrusters', meaning to turn on the thrusters. And lastly... To be engaged to someone means that marriage has been proposed and the couple is 'engaged to be married'. You'll also hear people say 'we were just engaged'. It means the same thing. Hope I can help!