www.drumcircles.net/Djembe%2...uning.pdf
Here is a link to one website that describes how to tune. This explanation tells how to put on a new head. You don't really need all of the info but the diagrams are good. If you scroll down the document it talks about "just Tuning".

Here is a simplified link
www.artdrum.com/DJEMBE_ROPE_TUNING.htm

And this one has actual pictures.
www.djembes.org/tensari.htm

I hope between the three you can derive enough info to make sense of the process of tuning. Its not as difficult as it seems. Give it a shot, you can always un-do what you don't like.

Good luck!