Here's how an If works.
If(booleanTest,True,False)
you put something into the booleanTest which can either be true of false.
So with my last formula, =if(AE30=0,0.2,if(AE30<=6,0.1,0)) I am testing AE30 to see if it equals 0, if so I put 0.2 into whichever cell my formula is placed in (AF30). If...