The majority of scholars view that the time for performing Ghusl on Friday begins from dawn on Friday. Doing it close to the time when you go for Jumu`ah prayer is better. However, one can read Surah Al-Kahf from sunset on Thursday until sunset on Friday.

In order to make complete ghusl, do the following: 1. Form the intention to purify yourself from major impurity: 2. Say Bismillah and wash the hands three times, then wash any dirt from the private part. 3. Do wudu as for prayer. 4. Pour water over the head three times, and rub the hair so that the water reaches the roots of the hair. 5. Wash the body, making sure that the water reaches all parts, starting with the right side of the body and then the left, and rubbing it with the hands so that the water reaches the entire body.

It is not permissible not to wash your hair during ghusl after sexual intercourse or periods. Therefore, you have to repeat the prayer. If your hair is braided, then it is sufficient to pour water over it thrice.