easy as that... for beginning you can macro your pet skills to your own skills to "micro manage" them...
f.e Bio with Egi standard-atk, Bane with Egi aoe-atk, Trisaster with con/blaze shield.

in the end it's simple as others mentioned above - put them on obay to cancel auto-knockback and use there skills like they would be your own. you can (and should) place them into your normal hotbar - the extra petbar sucks... : /