All this string stuff is giving me a headache!!

Can you guys help me out again. i'm basically trying to write a program that can search for word in a string. I enter some text into one text box and then enter the word to be searched into another text box and then i press find and i want a message box to come up saying "word found" or "word not found."
Also if possible can you tell me how to count how many times the word has been used.

If possible can you make the code as simple and beginner friendly as possible so i can understand it.

I've been struggling a bit lately, especially with the stings. Can anyone point me in the direction of any good websites or books that give good thorough tutorials about these kind of basics. I'm a bit embarrassed about always coming on here and asking you guys all these questions. I'm not freeloading or anything i am genuinly stuck.
The book i'm using has good questions but the examples and tutorials aren't in depth enough. They just skim the surface.

Thanks for your help.