What have you tried so far, and which part are you having trouble with?

There is some explanation in the program help.

Most Sage 50 tutorials have some budgeting walkthroughs. 

Be careful when buying a tutorial or looking at courses online that the material is specifically Sage 50 Canadian.   (not the American (Peachtree) or U.K. (Line 50)  software, which bear only a passing resemblance to Sage 50 Canadian.