Ah, I can help ye with this, but I'll be using m'phone to type this out, so unfortunately I cannot provide any illustrations. If ye got the correct coding as ye say, then y'er probably just missing something. First, let's start out with a checklist to see how things are fairing as of now and if that's not the issue then I would be happy to set ye on the right track of getting y'er transparent preset to work.
Check 1: Be sure that the file is exported as a .png! Ye may 'ave accidentally exported it as .jpg.
Check 2: Coding! May I see what y'er using as a transparency code? Even the smallest typo can break the code and not allow it to do its job.