First off, im not a welder, but I'll give things a try.
So according to the internet you keep cutting away until its shiny metal, trace this hole onto a piece of cardboard (kept the color theme going as best I could) cut it out and then get a piece of new metal to transfer the shape onto. seemed simple so far
I'm impressed with myself, and I also discovered the gas bottles for the welder are the perfect shape to for the radius of the curve. Some bystanders were not impressed at my discovery