Normally your toilet's water tank begins filling up with water immediately after you flush the toilet, allowing you to flush the toilet again once the tank has completely refilled. The water supply used by the toilet tank passes from the water pipe in the wall through the water supply valve, then the water supply line, which connects to the water fill valve inside the tank. You will need to troubleshoot the situation to determine why water is not refilling the tank.
Open the toilet's shutoff valve by turning the handle counterclockwise until it will not turn any more. Flush the toilet again to see if the tank begins to refill.
Twist the water shutoff valve clockwise as far as you can, shutting off the flow of water to the toilet. Take the cap off the toilet tank's fill valve, either by twisting the cap counterclockwise or by removing the screws on the cap and lifting it off.
Place the palm of your hand on the top of the fill valve, then slowly turn the shutoff valve's handle counterclockwise. Remove your hand from the valve and allow the water to flow out of the top of the valve for 30 seconds, then twist the shutoff valve handle closed and reassemble the toilet's fill valve.
Remove the fill valve's cap again and use a flathead screwdriver to remove the washer inside the cap. Press a new washer in place, reinstall the cap, then try flushing the toilet again.
Replace the fill valve if the tank still will not refill. Use a sponge and bucket to sop up any water left in the bottom of the toilet tank. Clamp pliers to the bottom of the fill valve inside the tank. Use a wrench to undo the nut connecting the fill valve to the water supply hose on the outside of the tank.
Use your hands to unscrew the locknut that holds the fill valve to the bottom of the toilet tank, then remove the fill valve. Measure the height of the toilet's overflow tube, then twist the top of the new fill valve clockwise, shortening the height of the fill valve until it is 1 inch taller than the overflow tube.
Install the new fill valve in reverse order of how you removed the old fill valve. Reconnect the water supply line to the bottom of the fill valve, then open the water shutoff valve to begin refilling the tank.