We, as Muslims, have to purify ourselves before offering prayer. Therefore, a Muslim is required to follow certain purification procedure known as wudu (ablution).

The Prophet (peace be upon him) said, “Allah does not accept prayer of anyone of you if he does hadath (passes wind) till he performs the ablution (anew). (Al-Bukhari)

But before ablution, you have to perform Istinja’ whenever one passes impurity from any of passages (front & back).

One can use either stone (tissue in modern times) or water. To perform it with water is preferred. The best is to combine both water and tissue, first by wiping with the tissue and then washing.

In this video, Sheikh Mohammad Al-Naqwi explains how to make wudu perfectly.