It is not necessary at this stage to teach them about consonants, vowels, long and short sounds and such grammatical constructs. Young children can learn to read just as well without these rules. By age four, most English-speaking children already have an excellent grasp of grammar of the language and in due time, they will learn all the formal grammatical rules in school. At this point, you need to concentrate only on developing the mechanical skill of reading. Teach your child writing along with reading.
Children learn to read faster and easier if they learn to write at the same time.
The motor memory of the letters, listening to their sounds and seeing them in writing will reinforce new learning. So, teach your child to write letters and words. Limit the initial reading vocabulary. Reading is a very complex process. Not all words can be read using simple phonic rules.