You can start potty training your child at 18 months. There are many potty training methods you could use. One way is to buy a potty doll and demonstrate with the doll how to use the bathroom. You can also have your child watch you use the restroom as well.
Potty train your kids as soon as theyt are able to sit on a potty tool with help of your support. I started potty training my toddler when he was six months old. You need to keep smallest and larger potty tools so that they are comfortably seated on them.
The later the better usually and not until they understand what you are asking them to do. It is simple once you start but be prepared to make it the focus of a couple of days, ask them constantly to sit on the potty.