Need to increase bowl water level. how do I do that

Step 1:

Remove the top lid of the tank, ...carefully, so as not to break the ceramic by dropping it on the floor accidentally. Inside exists a "lever" attached to a "float" acting as a "fulcrum," with the "float" resting on the level of the water in the tank. The more water in the tank, the more water will enter the bowl, at flushing time.

Step 2:

The level of water in the tank corresponds to the level of water entering the system upon flushing the commode (bathroom fixture). At the bottom of the tank exists a "flap" type of device (usually). As the water exits the tank into the bowl the flap seals off again, discontinuing the water's entry into the bowl. This should always seal off at the end of a "fllushing cycle." The more water in the tank at the beginning of the flush, the more will enter the bowl.

Step 3:

Therefore, raise the arm of the "lever" (sometimes it's a "vertical" post with an "adjustable float" on it; in what case one raises the float on the post, by depressing a "clip" like device on the float itself, sliding it up versus down) by bending the arm upward, ...carefully. The increased water in the "tank" by the above process should solve your problem. Be certain to note whether the "flap" closes prematurely (It shouldn't), adjusting the flap's "chain" (held up by the "handle" itself) should it close prematurely.

Step 4:

You may need to tighten the "nut" (fastener) on the "handle" inside the tank as the "chain/flap" may simply be closing prematurely, because it's "loose" (easily tightened by hand at times, versus with a small, adjustable wrench bought at a "hardware store" like "Ace Hardware").

Step 5:

The above items (one, versus several of them), should solve your problem.