How to insert text in to a word document from Rich Text Box

I have a rich text box in my c# application and it contains different lines of text(one to many lines). I want to get those lines and insert it to a word document with the font and the font size i want. This is how it should look like.

OBSERVATIONS:
• Line 1 from the rich text box
• Line 2 from the rich text box
• Line 3 from the rich text box

i want this to happen by using interop library.

i need some sample code for this since i'm a newbie