How to track expenses for digital products

Hi,

I have an Etsy shop and I am selling digital templates. I've bought a couple of graphics which I use in these digital templates. With my next question, you'll see I have zero knowledge about accounting.. 

How do I track the expenses for the graphics correctly? I use them now and include them in several templates, I can also use them again in the future. The templates with graphics I dont use anymore are still online and making sales. 

Appreciate every help, thanks!