how do I add (vanilla) tags to my own blocks/items?

Simple question: How do I add tags to my items/blocks, for example the tag "enderman_holdable" to make the block holdable for endermans? Furthermore, we've tried to make a type of soulsand ore, and we want the slowness and sinking effect  while walking over it. But I dont know how to give the soulsand-like ability to one of my blocks. Thank you for help.