I have strep throat and I kissed my fiancé. I did not know that I had it at the time. What show he do to prevent from get it as well?

Depends. The fact that u r aware that u have strep throat suggests u have been examined and may already be on antibiotics. In that case u r not contagious. If not then u shd have him gargle with salt water 3-4 times a day or with hydrogen peroxide gargles. If in spite of that he starts developing sore throat he wld need to see his doctor and get started on antibiotics himself. .
Depends. If your smooching happened before you were diagnosed & treated there is not much you can do. He may or may not get it as some seem immune or carry strep without getting ill. You may have got it from him. If he becomes symptomatic it would usually show quickly. He would then need to be treated.