Start with your upper back on the bench/box, plant your feet in the floor hip width apart and slightly step forward with one foot, the forward foot will be the "balancing" foot and the foot behind it will be the "working" foot. Engage your core and glutes as you press your hips up to about a table-top position putting a majority of the weight in the "working" foot. (3x10 per side!)

Beginner: Try just the bar first or dumbbells

Intermediate: 15-35lb plates on each side of the barbell 

Advanced: 45-90+lb plates on each side of the barbell

Modification: you can do these as glute bridges on the floor with a dumbbell instead