All you need to know to tighten and tune your djembe is shown in detail in these pages.
Djembe tuning isn't rocket surgery -it's a matter of tightening the rope (also called binding) to stretch the skin further over the drum head. The drum is then fine-tuned using what's called the Mali weave.
Beside sounding better, a tighter djembe also makes more sound, which is good news for your hands. Tuning requires a bit of physical effort though, so those with any physical conditions should go cautiously.
Jump to a link below or start with the step-by-step djembe tuning lesson.