My method is to just add half a cup of oats plus a cup of liquid (I tend to use oat milk or water, but any type of milk is fine) to a saucepan, bring to the boil then turn down to simmer for about 5 minutes, stirring occasionally. But do what works for you to get the consistency you enjoy.
The best part is the toppings! My favourites are a square of dark chocolate which melts in, maple syrup, cinnamon, chia seeds, nut butter and cacao powder or nibs but also any chopped nuts, seeds, honey or fruit work well or anything else you fancy!
If you really don’t have time to cook them in the morning, overnight oats are a great choice and can be completely prepared the night before. There are loads of great recipes about, I usually just mix half a cup of oats and half a cup of liquid (usually oat milk) to a container then add any of the toppings from the list above and leave to soak overnight. This can then be taken with you on the go.