This shampoo is intended as a regular cleanser for damaged or coloured hair. You can use it every time you wash your hair, unless your roots are very oily — in that case, alternate with a clarifying shampoo once a week. The source suggests pairing it with a matching balm or mask from the same series for a deeper conditioning effect. That means you can use the shampoo as the first step, then apply a conditioner or mask to the lengths and ends, leave it on for a few minutes, and rinse.
For best results, apply the shampoo to wet hair, massage gently into the scalp and roots, and rinse thoroughly. If you have very long or thick hair, you may need a second small amount for the lengths. After rinsing, follow with a conditioner or mask to replenish moisture, especially if your hair is porous or damaged. The shampoo itself contains conditioning agents that smooth the cuticle, but a separate conditioner adds more moisture and helps with detangling.
It is also fine to use this shampoo as a one-step product if your hair is not very dry — the conditioning agents in the formula already help with combing and frizz. However, if your ends are split or brittle, a balm or mask will provide extra care.