My sister has family subscription for apple music but i am not able to use the music on my phone.. how can i get acces to music. Do i need to make any changes to my account?

If you want access to her family subscription you will need to join their family so you are in the same family on Apple, ask your sister to go into settings and then tap on their Apple ID photo then scroll to the “ family sharing” tab and then set it up and tap add member, and add your Apple ID to the family and you should have access to Apple Music.