So first you will need this basic things
= Exp booster for your pet it will look like this...you can buy it from the pet merchant right next to the pet machine
= What you'll need to evolve you're pet, you'll have to buy it from cash shop.
"VP" it's the "Mana/EP" of your pet,used for hes' skills, the Experience of the pet is gain from this item→
↓ Now then, once your pets hit the full exp bar, like shown on the image bellow↓
Go ahead and -"DISMISS" YOUR PET-
After you "DISMISS" your pet just press the "Fusion" button on the rigth bellow corner like the one highlighted in red on the picture bellow, the "ok"
Then you get something like this , you choose a pet egg you probably dont want and just put it there
And here you go evolved pet with 2nd ability bar (at this case, the person got self revive and sell), as you see, you will gain 78 VP and you got a hole, and a new and longer pet exp. bar , then you're free to summon you're pet
To get lvl.3 you probably will have to add the Item (), and then press ok, as shown on this picture bellow.
--U WONT NEED IT FROM LVL1 TO LVL2--
The Pet evolutions will look like this:
Easy and awesome right?
Glad to be of help!