It's running Android 7 so you should be able to nominate the SdCard as either Internal Storage (for Apps which can work outside the system folders; many cannot) or Portable Storage which allows you to move all your pictures, music, etc. It's a one or the other choice.
It's also a one-off non-reversible choice so give some serious thought before taking the decision. The place to go is by tapping the Apps square to get to Settings then More>Storage.