Yes — the product is described as a hair and body soap, so washing the scalp and hair with it is an intended use, not a workaround. It is soap-based rather than a standard liquid shampoo, which matters in practice: soap lathers differently, especially in hard water, and it cleans more intensively. The formula is aimed at oily scalps and at removing oil and styling residue, so if that matches your situation, work the lather into the roots and then let the leftover lather run down the lengths.
Because it is a soap, the hair may feel drier or rougher after washing than it would after a mild shampoo. The jojoba extract in the formula is included to reduce that over-washed, rough feeling, but it is not a conditioner. If your lengths tend to be dry, keep most of the washing on the scalp and use a conditioner or a small amount of hair oil on the ends afterward.
There is no requirement to use it every wash. A common pattern is to use a tar soap as a periodic deeper cleanse and keep a regular shampoo for the rest of the week. For color-treated, very dry, or easily irritated hair, the source advises alternating with a milder cleanser and watching how the hair and skin respond. Lather it in your hands first rather than rubbing the bar straight over the hair, massage the scalp, rinse thoroughly, and keep lather away from the eyes.