help integrating pit mix pup with a heeler old lady....

am new to this group....but i have recently acquired a 3 - 6 month pit mix and have a 6-7 yr old heeler - both females.....the baby seems to have a predisposition to possessivness? not sure of her life before i found her but has decided i'm her human =)

she needs obedience training n such and will look for it here (small town) but need help getting these 2 girls to learn to live with each other!

thank you for any help provided!