Open the “Settings” app.
Scroll down to the bottom and select “About device“, “About phone” or “About tablet“. On some models, select “General” before this step.
Scroll down to the bottom and tap “Build number” repeatedly. A message should appear on the screen that says, “You are now * steps away from being a developer.” Keep tapping until it says, “You are now a developer.“
Now back on the main “Settings” screen, “Developer Options” should appear as a selection.

Ý bài viết trên là touch, giữ, touch cái build liên tục xong, làm tầm 4, 5 lần cho đến khi ra thông báo