Need more info. Biggest question, what background color is it to be used over? Second, does there need to be any white in the graphic?
If to be used over a light colored or white background, making decal is easy. Just size properly with a paint or photo editing program and print on clear decal paper. Coat with a protective coating. Then cut out decal and apply like a store-bought decal.
If you are applying over a dark background, you will need to use white decal paper. Now, the problem is you either must cut the decal from backing with super precision to prevent a white border, or you must set the background for your graphic to the color over which you are applying the decal. However, for many colors matching the printed color to the background color can be a major PIA. Calibrating monitor and printer can be done but is not that easy and requires hardware. Black is easy to match, primary colors some problem but maybe doable. Non-primary colors are a real problem.
Some printers work better than others when it comes to color matching and high saturation.