The question is to be answered on a physical and spiritual level. On a physical level, you should have some prior knowledge of asana practice. This does not necessarily have to be from the classic yoga studio, but can also be taken from other sports.
From a spiritual perspective, yoga is a lifestyle that incorporates elements such as conscious breathing, mindfulness, contentment and compassion. That is, maybe you already practice yoga. If you have signed up for yoga teacher training, just prepare yourself with some yoga poses and our recommended books.