Well I'm assuming you don't understand the composite/prime number business either. So I'll break it down shotgun style.
Find the sum of every composite number (number that's not prime). 8 + 4 +6 + 9 +4 = 31
Find the sum of every prime number (number that's divisible only by 1 and itself). 2 + 3 + 5 = 10
Multiply together. 310
Take the first 25 non-numeric characters and increase their ASCII value by one. abyuopkvcss = bczvpqlwdtt --check out an ASCII chart here
Concatenate that to the product. bczvpqlwdtt . 310 = bczvpqlwdtt310.
Then you have to write a script to do all that smoothly and submit it in the form on the page pretty quickly.