You'll need to convert the artwork into a vector first. There's an option at the top for you to do this. It's called Image Trace. You can even pick from the drop down beside it, to set the quality of the trace. After AI is done tracing, you can click on the image again, you will see that Image trace option is not there anymore but there is an Expand option. The Expand button sets the points on the vector so you can edit the points with a pentool.