I'd suggest lots and lots of practice. Make it a habit to read (even if it is only a little bit) every day and practice with someone older who knows how to read. There are lots of worksheets on Education.com with reading and spelling/vocabulary help. They are listed below. Good luck!
When my sister needs to study for her 6th Grade spelling test, she looks over the list of words and I quiz her that way.
If she's having trouble with a particular word, for example the word "indestructable," I will help her break the word up in syllables and she learns it that way. So, for this word it would be broken up to: in-des-truct-able. Sometimes it's easier to remember how to spell a word when you learn it in pieces rather than the whole chunk all together.