Every chord starts as a major seventh chord. Use the arrows to lower or raise its notes until it becomes the chord asked for, and watch the scale degrees change (3 becomes  flat3, and so on). Those formulas are what to memorize.

Chord	Formula
Major seventh	1 3 5 7
Dominant seventh	1 3 5  flat7
Minor seventh	1  flat3 5  flat7
Half-diminished seventh	1  flat3  flat5  flat7
Fully diminished seventh	1  flat3  flat5  double flat7