Forget everything you know about the Trojan War. First of all, the Iliad is not supposed to be a history of the Trojan War. It's an account of a few days in the course of a ten-year war. Secondly, the Iliad is not an authoritative history. It was one of many competing legends. The Iliad is an amazing story. Don't try to make it something it's not, a history of Mycenaean Greece. Read it as a tale of heroism, jealousy, beauty, honor and, above all, people.
Find a good place to read. Everyone has a preference about where they most enjoy reading. It might be outside under a tree or in a large armchair in front of a fire; it doesn't matter as long as you like it. Go to this place where you feel comfortable, give yourself some uninterrupted time and just read.
As you read, imagine the story being told. The Iliad was originally an oral poem. Imagine being a palace in ancient Greece, in the audience of an open-air auditorium, or sitting around a campfire in the hills of Attica while a bard recites the entire poem. Look out for mnemonics, devices that helped the poet memorize the entire poem and keep the meter, such as "Hector, breaker of horses," which occur repeatedly throughout the poem.
Pick a favorite. Don't just read, engage with the poem. Who do you want to win the war? Would you have wanted to be a Greek or a Trojan? Who is your favorite hero? Is it Achilles, with his strength; Hector, with his honor; or maybe cunning Odysseus? Don't look at the events as having happened thousands of years ago. Look at them as something alive that could possibly change.
Let your imagination run. Imagine thousands of soldiers standing under the towering stone walls of Troy. Hear the creak of wooden wheels as chariots race by. Listen to the shouts, the noise of thousands of men battling to the death. Taste the dust kicked up by their feet. Smell the fear and adrenaline in the air. Let the screams echo in your head, as heroes fall to their fate on an abandoned plain before a glittering city.
Daydream. Don't just imagine the battle before the walls of Troy; imagine yourself in the battle before the walls of Troy. Be Hector, standing before the imposing gates of your home and the eyes of your citizens, watching the godlike Achilles stride towards you. What would you have done?