Eat with your right hand, even if you’re left-handed; many families teach left-handed children to eat right-handed specifically for this reason. If you need to steady a plate or serve yourself with a spoon, the left hand can assist, but food itself goes from right hand to mouth.
The left hand isn’t fully benched, though: it’s fine to hold a glass of water, or use it to help tear a piece of roti or chapati in two. What it shouldn’t do is touch food that’s about to go into your mouth, pass a dish to someone else, or wipe your mouth.
The same right-hand rule extends to handing over money, gifts, or documents, use your right hand, or both hands together for something formal.