Now, go to the next open number.  Since 2 and 3 don't go in, it must be prime!  Circle him and cross out all of the numbers he goes into.
 

A grid of the numbers 1 - 100  ...  circle the 5 and cross any other numbers that 5 goes into.

 

Can you finish it off?

Here's the final thing
 

A grid of the numbers 1 - 100  ...  circle the 7 and cross out any other numbers that 7 goes into.