You might begin by expressing the idea that, for Irenaeus, evil is meant to serve a purpose. It is key to understanding Irenaeus that his theodicy can be described as ‘soul-making’ rather than the ‘soul-deciding’ theodicy of Augustine. You could point to Irenaeus’ use of Genesis 1:26, where God is described as wanting to make man in him own ‘image and likeness’. This means that we may be born in the image of God but we must grow, throughout history, into his likeness. Irenaeus would argue that God intended humans to mature over a lengthy time, sending his own Son as a part of this learning process. Evil is therefore sent as part of this maturing of humanity; without evils such as death and other pains, we would not learn the need for goodness and repentance.
For Irenaeus, humanity needs to be patient, much like the clay in the hand of a potter, one of his favourite images. However the clay that is humanity needs to work with the potter and not harden to the work and be discarded. The idea that everyone will eventually be saved seems to be a later interpretation that is not found in Irenaeus’ own writings.
This question is at the root of all theodicies and therefore you could evaluate any in your response. Many students studying this course will focus their response on either the Irenaean or Hickian versions and this is fine but you do not need to be limited. If you want to argue a benevolent God exists, then you need to assess whether or not our experience of evil can be explained by any philosophy. Make sure you do not just write out some theodicies, but accurately assess their success in justifying a good God.