Google is your friend: Be nice and visit him often. He can answer questions a lot more quickly than posting them here...
A very quick search
using a chunk of your question as the search term gave nearly 3/4 of a million hits:
Google "automatic backup of SQL database"[
^]
The top "non-ad" hit is MSDN describing how to do it:
http://support.microsoft.com/kb/2019698/en-gb[
^]
In future, please try to do at least basic research yourself, and not waste your time or ours.