As long as it's for the bees, and not for human consumption, you don't need to worry about what's nectar and what's syrup. The bees will eat some of either on the spot and convert the rest into honey. Obviously you wouldn't want to sell honey that's made while you are feeding.
Feed your package in the spring until you see capped stores. Capping means they have enough that there is a surplus. Stop feeding when you have at least a frame of capped stores. Put honey supers on before/during the main flow. Don't feed when your honey supers are on. When the main flow is over, decide if you want to harvest any honey from your supers. You can leave it all for them if you want. Then figure out about what weight you need the hive to be at to make it through the winter. Other beekeepers in your area can help you figure out what the weight should be. Then feed the hive until they make weight. If there is nectar available, of course the bees will keep gathering and reduce the amount you have to feed them. Once you have the desired amount of stores for the winter, you can stop feeding again.
In short, feed when the bees need food. If they don't need more food, don't feed them.