Ok well if your ds has not started school and you haven't accepted a place yet, then you don't really need to do anything. You can get in touch with the LA and tell them you intend to H.ed However, if you have been offered a place or attended school you need to deregister. This is a simple letter to the school telling them you no longer require the place and intend to H.ed
I am unable to link here but there are lots of useful websites that you can find on these threads and in terms of resources they are freely available online, you needn't spend lots of money.
If you have specific questions there are many knowledgeable people here who are happy to help, so do post your questions, even if they seem silly. We have all been there, and I gained so much from talking to people here.