Hi Judi
You can disable comments across your site in the Wordpress Dashboard.
At the bottom of the left menu click on
SETTINGS > DISCUSSION
Uncheck the following two options:
[ ] Allow link notifications from other blogs (pingbacks and trackbacks.)
[ ] Allow people to post comments on new articles
That will disable comments and remove the comment box from any new posts.
To remove the comments / comments box from existing posts you'll need to batch-edit all your posts.
POSTS > EDIT
Then hit the select all check-box, select edit from the drop-down menu, and hit apply.
Change Comments to "Do not allow"
Hit Update Posts.
If you have a lot of posts you'll have to do a batch edit on every page of posts (unless someone knows an easier way to batch edit all the posts at once).
Hope that helps.