Apply grease on the other bearing balls, and put it onto the spindle with the bearing cage facing outwards.

Apply a generous amount of grease to the inside of the left side bottom bracket cup.

Put a light amount of grease on the threads of bottom bracket cup, and screw it into the shell by hand.

Adjust the tightness of the non-drive side cup until the spindle spins freely without resistance, but all of the play is eliminated from the spindle. If the spindle moves up and down, you want the cup more tight, and if the spinning doesn't feel smooth, you want to loosen it a bit.