These are general hygiene practices that people follow in the United States.
The toilets in the United States are above ground and have handles to flush them. The toilets are also usually inside unless the toilet is a Port-a-Potty. A Port-a-Potty is an outdoor toilet that does not flush and does not have a sink. If you use one, make sure to lock the door behind you and use the hand sanitizer when you are done. You will not need to flush when using this type of toilet.
In public restrooms the toilets will be inside and you must flush these toilets. Some toilets will flush automatically but not all of them do this. In public there are typically different restrooms for women and men. You can tell which one to use by looking at the words written on the bathroom door or by looking to see if there is a picture of a man or a woman on the door. Some places have gender neutral bathrooms which means that there is only one toilet in the bathroom and that both women and men can use this bathroom. Every bathroom will have a sink with soap so that you can wash your hands once you are done. Many public bathrooms will have a table where you can change your child's diaper. Make sure to properly dispose of the diaper in the trashcan.
Every home will either have a shower or a bathtub. Some homes will have both. In a shower you will stand up and the shower head while you shower and the water will come from above you. You can control the temperature by turning the knob left for hot water and right for cold water. In a bath the water will come out from a lower place called a faucet. You will need to close the drain so that the faucet water can fill up the bath tub. The bathtub will also have a knob that you can use to adjust the water temperature. Make sure to drain the water when you are done. You will probably want to have a towel nearby for when you get out of the bath or shower.