You can still meditate properly if you have ADHD. Some people find that by taking their prescribed medication for ADHD treatment, they are better able to focus on meditation. Others find that meditation acts as a type of treatment itself for ADHD. Like anything else, meditation takes practice.
If you are someone with ADHD and you are trying to meditate and are finding it difficult, do not be discouraged. Keep trying and practicing until you find a method that works for you. Experiment with different settings and different times of the day. Even with ADHD, you will find it is possible to meditate.