How to Defeat the Eye of Cthulhu?

So, I've been playing Terraria on mobile for a bit now and I have come across an item called Suspicious Looking Eye. I've collected a couple of them already. This item looked like it was really of no use. I tried it out during the day but nothing ever happened. But then, I experimented with some items and tried to use it at night... and Voila! the Eye of Cthulhu magically appeared right in front of my mobile screen! Being unprepared, I was obliterated in an instant.

Do you guys have any tips for me when fighting this boss? This is actually my first boss battle in the game and I seem to not know what to do. I've been looking at some guides, but i cannot really follow their tips.