In the Anime, during the Chunnin exams, Orochimaru attacks Sasuke inside the Forest of Death. When Naruto came to rescue, Orochimaru identified that he was the nine tails and places the Five Elements seal on Naruto. Later it was unsealed by Jiraiya. In the Search for Tsunade arc, Orochimaru tells Kabuto that the seal can be placed or removed only by the 3rd Hokage and the sannin. Were the 3 sannin taught about this by the 3rd Hokage?
Apparently so. It's possible that other people were able to use the seal (for instance, Kushina, who was a sealing expert, or the Second and First Hokages, who knew advanced sealing techniques, but passed away).
It's possible that they referred to only living shinobi for that purpose (it makes sense, because they were trying to figure out who unsealed it).
I believe the technique was passed down to (or invented by) the Third, and he in turn taught it to his disciples.
Note that Minato never used the Five Element Seal.