I'm assuming you are referring to files with .doc or .docx extensions (and even maybe .rtf or .rtfd).
In Finder, select one such document file (don't open it), CMD+I to 'Get Info'.
In the Get Info popup, you should see an option "Open with:" (if you can't, click the little triangles to expand each option), with a drop-down menu. Choose your preferred Word Processor in the drop-down and then click the Change All button to make that default to all documents of that type.
Repeat for the other file types as necessary. You may have to Relaunch Finder if the file doesn't open with the new application (rare though)