Do I use the genetic mutator

The genetic mutator changes a gene. Use it through a pet's profile page, click on the "philters" button (i think that's what it's called)

Okay thank you I'll try

The genetic mutator is actually a philter that adds a trait to a pet. Lesser ones can add either a carry or visible on an empty trait slot, and greater's can add a visible of your choosing on the pet. However, it only works on tamed creatures that you catch, so bred and exclusive sylesti's cannot be genetically mutated. You can also only genetically mutate a pet once. As Orca said, you can do this by going to your pet profile page, clicking the genetic philter button.