Well, I unfortunately dont have any advice for teaching your child to type, but before you do that, you may want to make sure your child understands that there is a connection between symbols and their real life counterparts. Words are symbols that represent real life things. For example 'food' is just 4 letters, but it represents something that you can pick up and eat. Prior to teaching your child to type, you must first teach them that symbols represent items. After that you can then start teaching your child simple words and show her how to type them out.
You might want to start off with something called PECS. It is an acronym for Picture Exchange Communication System. Basically it is just pictures with words on them that you cut out and use for communication. Its basically like sign language, but with pictures instead of hand signals. If you want more information, try googling PECS. You will find plenty of information on there.
Also, welcome to the web site. You may want to browse some of the other posts and see if you find them helpful. And feel free to ask any other questions you may have.