Wash with a clarifying shampoo and towel-dry your hair. Mix the toner with developer if required - always check the instructions on your specific product. Then apply to damp hair in sections. Start at the mid-lengths, then move to the ends, leaving the roots for last. Process for the time listed on the product, then rinse, shampoo, and condition. Toner is simply another name for colour, often used after lightening, and is also known as a glossing colour for darker tones.