Does he know the letter sounds? This is what he needs to know next. Letter names are not important yet.
And then you can move onto sounding out simple CVC words such as cat, dog, hat, etc.
Then add blending sounds such as sh, th, ch, ou, oy, ai, ee, oo, etc.
You then look at words like toy, book, bee,
Some words are taught by sight - search out the reception key words. There are 45 of them. Include words like the and you.
You then look at how letters can sometime make alternative sounds, often because of some for of rule - such as the magic "e" on the end of a word changing the way the preceeding vowel is said.
Lower case letters more important than capitals in early days too.
I am sure someone more knowledgable will be around soon. This is just what I have picked up from DD.
Look up Jolly Phonics. They offer some good advice on what order to approach things.