Check out any of these for 2.8 texturing guidance:
However, understand that these were both recorded while 2.8 beta and some aspects of current 2.8 may be different.
Later on, you're likely to save your image texture to a file in #1 and/or may reference a file with Open in #5.
Thank you. I hope this gets into the 2.8 tutorial if they ever remake it. :3