To write a letter, a book, a thesis or a simple "No Smoking" notice, you need a word processing program.
These lessons are referring to the most known program: Microsoft Word - 2007 release.
Another word processor is Open Office - Writer (free) very similar to Word.
Step 3.1 - Knowing the window of the program
Step 3.2 - Knowing the keyboard
Step 3.3 - Saving, closing and opening the documents