Well I can't tell you how to program, but I can give you some simple commands you can use. There is also a help section in the editor, where you can write in commands and it will explain how to use them.
Are there any commands you already know, so I'm not giving you obsolete information?
Before getting into games, I suggest starting in the text. What I did is look at the SmileBASIC manual then try to code basic things. I also look at examples and ask people from Miiverse what to do. I also sometimes type a few letters, choose a command, and look at the help menu to see what it does.
maybe you can make a simple movement game with BUTTON() as input to move a little space ship letter using this code:
@LOOP
B=BUTTON()
IF B==1 THEN Y=Y-1
IF B==2 THEN Y=Y+1
IF B==4 THEN X=X-1
IF B==8 THEN X=X+1
CLS
LOCATE X, Y, 50
PRINT"O"
WAIT 1
GOTO@LOOP
modify the code and see what happens.. B, X and Y are variables. They have a number or word stored. Imagine a variable as a drawer with a
sign with the name of the variable on it. When you type something like X=1+2 then the computer will calculate the math and place the result in the drawer. X=X+1 means, if X is 5 for example, that you take X, see that it´s '5'. Now it will add '1' and get 6, now 6 gets put into the drawer again.
I know this all can be complicated, but if you really think about it, you will get every problem solved!