I have the nfz puffer can I use it on my 2 little 2 week old kittens, that have yellow crusted eyes?

Personally, I am not that familiar with this product. As I understand, it is a treatment for pinkeye in animals, however at 2 weeks old I would not recommend using it in a kittens eyes without first consulting your Vet.
Is the mother around? She should still be keeping them cleaned up.
If she is not doing this I would suggest a warm cloth to soften the crust and remove it carefully, without applying too much pressure on their eyes.
Of course, you will have to be diligent and keep them clean.
If there is infection present, you can safely use an ointment that is made
Especially for the eyes that your Vet can prescribe.

As usual, LadySam has given good advice.

NFZ is nitrofurazone, normally used as topical antibiotic for open wounds and sores. While many suggestions for it's use in eyes are made, I have found that medicines formulated especially for use in eyes are better received by the patients. Pink eye is a contagious bacterial condition and not likely what your kittens have. Take a warm tissue moistened with water, and soak as Lady Sam suggests. At 2 weeks old the kittens eyes should be open or opening. This problem is common for kittens and pups who don't get their eyes completely open. It's usually a mild infection of the lid margins. In fact, it is so common that it even has it's own 'name', and is discussed at this link:

http://www.petplace.com/cats/ophthalmia-neonatorum-in-kittens/page1.aspx

Seeing your vet for any problem you may bring to us is always a good follow-up idea.