how do I get non festival essences to generate regular, enhanced generated and other pets?

As far as I am aware, you can't convert or change one into another. You can trade one for something else more suitable for your liking, but you can't do the forementioned action of changing it into something else. Festival essences create festival pets, regular essences make regular pets, and enhanced essences make enhanced pets; you're going to have to trade to get whatever you want.

As opposed to the Frost Essences found by participating in the Winter Festival, normal Essences can be obtained in multiple ways:
Definite:
> Buy from Diamond Shop (best to do when there's a Sale on)
> Buy off of Trade Broker (varies by users, price varies by pet species and whether it's a Regular, Enhanced, or Mystical Essence)
> Obtain from an Item Trade thread.

Chance Based (Rare chance; Regular or Enhanced Essence):
> Battle (will give essence of defeated species)
> Nurture (will give essence of nurtured species)
> Mission Satchels (random)
> Jinxie's Jamboree (random)

Other:
> If you have a design picked in a "Design a Gene/Mutation" thread, you will get a Mystical Essence of the species it the Gene or Mutation is implemented on.

Unless the question was about how to use them? It is a bit hard to tell by the phrasing of the question

it was actually how to get them and where to get them so you got the correct info for me thank you :D