HOW TO EDIT A VECTOR IMAGE!

HEY! I NEED SOME HELP!

Does anyone know how to edit the colours of a Vector image on Corel Draw??

I've downloaded a Vector Image from ISTOCK and i should be able to edit it and change the colours but i have no idea how to do that!?! What do i need to do to the image before i am able to edit it?

Please let me know ASAP! As im at a standstill at work until i figure it out!

Thanks! :)