Here are some possible ideas to get you started. I would consider using the opening lines to show the environmental conflict-
Bent double, like old beggars under sacks,
Knock-kneed, coughing like hags, we cursed through sludge,
As many of the soldiers died due to the conditions rather than as a result of direct combat this is an important point.
To signify the physical conflict I would use the gas attack and the soldiers’ panicked response-
GAS! Gas! Quick, boys!-- An ecstasy of fumbling,
Fitting the clumsy helmets just in time;
For the psychological conflict I would refer to the challenge of the gas attack and the trauma of seeing his colleague die, and the image returning to the narrator’s dreams-
Dim, through the misty panes and thick green light
As under a green sea, I saw him drowning.
In all my dreams, before my helpless sight,
He plunges at me, guttering, choking, drowning.
Finally I would use the emotion of Owen’s challenge to Jessie Pope and the other propagandists which concludes the poem-
My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori.