How does one use the emblems and at what level can one use them?
The emblems have been around for nearly 2 years now. Here is a link to the announcement which I believe also addresses many of your questions.
Also, here is a guide for hero classes and class quests (which came out at the same time).
Hope this helps you.
Simply put when you max level a hero you can use emblems, theyre somewhat rare so best to wait for a 4* or 5*, don’t waste on a 1*/2*/3*
Thank you! I appreciate your reply!