Center 1: two pieces on the opposite face
Step 1 / 4
x': Whole cube: turn 90°, front face goes down
The top is missing two spots in its right column: back and middle. Two white pieces sit on the bottom, in the row next to the back, left and middle.
x' brings white to the front and the bottom to the back. r2 parks the front's right column at the back, B' turns the white pieces into it, r2 brings them forward.
Step 1 of 4: x'. Whole cube: turn 90°, front face goes down