clara
I'm not an insulin user, but have been married to one for near 36 years. Ideally, you should check your Bg level before eating and estimate the carbohydrate you are about to eat. Hopefully you will learn how to do this soon.
Then you take your insulin and eat straight afterwards. If your level is fairly low before the meal,( 4 - 7) then waiting can be dangerous, but if it's high, say over 10, there's not much risk if you don't wait too long.
I would certainly advise you to learn to count carbs as soon as you feel able. It's a lot when you are still coming to terms with the situation, but your most powerful tool.
good luck
Hana