Even though scoring all vitamins and minerals is essential for healthy living, not all of them are synthesized by our body in the same way. Hence, one must pay attention on how you have them.
While Vitamin C is a largely helpful nutrient, it is a water-soluble nutrient, which is best absorbed when you take them empty stomach. An ideal way would be to take your supplement first thing in the morning, 30-45 minutes before your meal. If you plan to take your Vitamin C later in the day, make sure there is a good gap after your meals so that it gets absorbed well.
Another way to match up on your requirement is to have a Vitamin -C rich diet, which you can have through the day.