macbook rejects user name and password

Hello, the macbook has a two account and my account not the main account. That's the reason i dont enter the illustrator that i dowlaoding the app. Because it wants me to the user name and password but not my account, it wants to the other account. I didn't solve this problem. How can i delete or enter the other account? I researched on mac page but it didn't work. So i can't use the illustrator.