Again, you should leave the F3 function turned on during the entire puzzle. This is a function you can easily duplicate on paper and pencil, adding numbers to the side, bottom or ovals as the number of slots still to be filled in a row, column or box drops below six. Then, as you fill in more slots, you can cross out the numbers that are no longer necessary. The only difference here is that the program will do the bookkeeping for you.
For example, in the puzzle below, notice that the left bottom box has a 4 in it. This eliminates the two empty squares from the 2nd column that are also in this box from having a 4 in them. The 5th row also has a 4, eliminating the empty square in the 2nd column that intersects the 5th row. So no 4 can go there either. Thus, the only remaining empty square in the 2nd column MUST contain a 4. After placing that 4, similar reasoning locates a square for a 4 in the 8th column. And so on.
You should continue to use the methods you learned in the first exercise and the hints supplied there.