Here is a great way to enlarge and transfer a study drawing to your canvas. It’s one of many ways to do this, of course. You can also use graphite or charcoal transfer paper, or you can project your image. I’m sharing this method because a lot of people don’t know about it and it’s probably the most archivally sound method of transferring a drawing. I learned this method from a great artist and teacher Douglas Flynt. The advantage of an oil paint transfer is that it’s just paint. You don’t have to use any unhealthy fixative or worry about the graphite eventually migrating to the surface (you may have seen this phenomenon in the museums from time to time).
Once your drawing is transferred and dry (24 hours should suffice) you can proceed as you like. Many people will do some sort of grisaille or underpainting before tackling the real business of the painting. An underpainting is my usual method and highly recommended.
One other thing…since this process can sometimes involve a fairly large dollop of paint, I suggest using a cheaper student brand such as Winton, made by Winsor & Newton.
Below is an image of the finished painting, “Paris”, 36×24, oil/canvas: