Expert puzzles require a patient candidate-by-candidate approach. Keep the grid tidy and test each elimination against row, column and box constraints.
Experienced players who already use notes and basic box-line reasoning.
Find two cells in the same row, column or box that contain exactly the same two candidates. Those digits are reserved for the pair, so you can remove them from other cells in that unit.
On a keyboard, use the arrow keys to move between cells and N to toggle notes. Read the beginner guide or try a worked naked-single example.