I'm not very experienced in dieting and I can't really set the right amount of the small portions of food I should eat 6 or 7 times a day. I'm 6'2 , 170lbs (183, 77 kgs) , and for one portion I ate one skinless chicken breast, is one average sized skinless chicken breast too much for one meal. How should I know how much lbs or grams of meat or food to eat on one meal.

Each meal should be the size of your fist

so the whole meal should be the size of a fist? Like 2 bites broccoli 2 bites potato and 4 bites chicken?

That's going to be way too little food. Look at the calories. You need to calculate how many calories you can consume in a day, and then divide that number by six to figure out how many calories you can have per meal.

that fist rule is very dubious and shouldn't be used in my opinion. One fist full of peanuts will have way more calories than 4 fist fulls of celery.

Find the calorie value of the foods you're eating, one chicken breast by itself doesn't constitute a meal