It's pretty easy to find, here's my quick guide:
In Leeds city centre, follow signs for the Universities. You'll be going up a long, fairly straight road (Otley road, I believe). You'll pass Leeds Met (on your left) first, across the road on the right should be a boat (it's a pub!).
Further up the road you'll see a beautiful tall white tower and building. This is the Parkinson Building, it's the most central bit of Leeds University. You can't park up here but this is where you want to reach on foot.
While facing the Parkinson Building outside the steps, go left and follow the road down so you go past a church on your left. There should be a big construction site coming up in front of you. Walk past that so it's on your right. The row of houses just beyond it and also on the right is the School of English. The main entrance should be clear but basically it's the final house on the end of that row of buildings. Good luck!