Usually centering you bicycle hydraulic disc brakes takes care of pads dragging on the rotors. If it doesn't, there are typically two other issues to look at, which I show in this video.
How to center hydraulic disc brakes:
https://www.youtube.com/watch?v=j_-sv94eQ4E&t=27s
How to center brakes with the Birzman tool:
https://www.youtube.com/watch?v=hBdJYX8tICA
How to bleed Shimano mountain bike brakes:
https://www.youtube.com/watch?v=QciJbZf6Bqc
How to bleed Shimano road brakes:
https://www.youtube.com/watch?v=SMGl58-tMqg
How to bleed SRAM road brakes:
https://www.youtube.com/watch?v=2mxzFomRYNg
How to bleed SRAM brakes with Bleeding Edge tool
https://www.youtube.com/watch?v=A8J3QGwHZjI
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