The nice thing about etching on a glass is that you can pretty much use any high contrast pixel image. You don't have to turn any line into a vector.Cleanup In Photoshop
So basically, I imported my (low resolution) image that my friend texted me from her Iphone into Photoshop.
I opened it in Photoshop, used the magic wand tool to remove the tan background, zoomed into clean up the edges with the erase tool.
Import the image into Illustrator
I imported the image into Illustrator. When you open illustrator you want to make the canvas size the same as the surface area of your glass. I'll talk about that in the next step.