The following is a tutorial on how I install an editor in Drupal 7. For this example, I'll use TinyMCE: www.tinymce.com
1) The first thing to do is to install and enable the WYSIWYG (what you see is what you get module).
go to: http://drupal.org/project/wysiwyg
With WYSIWYG installed and enabled, go to CONFIGURATION >> CONTENT AUTHORING >> WSIWYG PROFILES, locate TinyMCE in the list of editors. Note the figure below.
Fig1.
2) download TimyMCE 3.5.8 from: http://www.tinymce.com/download/download.php
Extract the archive and copy its contents into a new folder in the following location:
sites/all/libraries/tinymce
So the actual library can be found at:
sites/all/libraries/tinymce/jscripts/tiny_mce/tiny_mce.js
Note: you might need to manually create the libaries DIR if you dont have one. Note, place the extracted tinymce dir exactly as prescribed above.
Go back to CONFIGURATION >> CONTENT AUTHORING >> WSIWYG PROFILES, locate TinyMCE in the list of editors. Note the figure below, showing TinyMCE properly installed:
Fig 2: 
3) Configuration: still at CONFIGURATION >> CONTENT AUTHORING >> WSIWYG PRFOILES, select an editor for a text format type. Presently, I have selected TinyMCE for Full HTML.
Fig 3:
Dont forget to SAVE!.
Now, edit Full HTML to add some functions: click EDIT >> BUTTONS AND PLUGINS to add some functions to the editor:
select some functions to add, don't forget to save.
Now, lets go back to a text field of a content type and set it to use Full HTML: STRUCTURE >> CONTENT TYPES >> BASIC PAGE >> MANAGE FIELDS: edit the "body" field and select FULL HTML as default text format value, Save Settings.
Now create a new content content type(ex: Basic Page):
thats all folks!.
Note: it is possible to have different text-formats for different user roles. To do this, a user role must be created first and assigned proper permissions. Then create a new text-format and assign it to the newly created user role. Then, just like Fig-5(above), select editor functions for the specific user role.
Questions, comments and clarifications welcome!
