The setting names vary based on the version of macOS you're using:
- Choose Apple menu > System Settings (or System Preferences).
- Click Accessibility.
- Click Pointer Control (or Mouse & Trackpad).
- Click the Trackpad Options button.
- Turn on “Use trackpad for dragging” (or “Enable dragging”).
- From the pop-up menu, choose the “three finger drag” dragging style.
- Click OK.