New and have not much understanding of autism! Help!

I am 28 yrs old and my 3 and a half year old son just got diagnosed with autism, hes just started nursery and im so scared and nervous about it all! Its so daunting and cary! I suffer from depression and anxiety and have done for years! Had really bad pnd also! I have a 1 year old too so its all so hard to juggle! Since ive been told my eldest has autism ive been on a different planet! I dnt understand! I dnt know how to deal with it! What if i fail! What if i cant help him! What if he doesnt get enough help! My son is so so so intelligent its just his behaviour! I dnt understand autism much! I just need help and support and have no where to go or get it from!