First, I assume you mean Windows 10, not Microsoft 10.
There are many ways to type a letter. Here are some of them:
- Use Notepad, which comes with Windows. Notepad is really a text editor, not a word processor, but if your formatting needs are slight, it may be adequate for you.
- Use Wordpad, which comes with Windows. Wordpad is also really a text editor, not a word processor, but if your formatting needs are are greater than what Notepad provides but still slight, it may be adequate for you.
- If your formatting needs are greater, obtain a real Word Processor:
a. Buy and install Corel WordPerfect, the best word processor, in my view.
b. Buy and install Microsoft Word, either by itself or as part of Microsoft Office. It's the
most popular, but In my opinion, not as good as WordPerfect.
c. Download and install either the free OpenOffice or Libre Office. Both
are largely (but not completely ) compatible with Microsoft Word.
d. There are other choices of word processors, but I have no experience
with any of the and can't recommend any of them.
My recommendation is to forget about Notepad and try WordPad. If it meets your needs, great. If not, go for one of the choices 3a, 3b, or 3c. I recommend 3a, but the choice is yours.