Connect Supply Line and Fill Tank

What happens here

Now, connect the new braided flexible stainless steel supply line to the fill valve on the underside of the toilet tank. Hand-tighten the connection first. Then, using an adjustable wrench, tighten it one to one-and-a-quarter full turns past hand-tight. Avoid overtightening to prevent damaging the connection or the fill valve. With the supply line connected, slowly turn the main water shut-off valve counter-clockwise to open the water supply. Allow the tank to fill completely.

Goal: Restore water supply to the toilet tank.