First you will create a frequency table then you will list each other before 0-4 5-9 10-14 and 15-19 that will go in the first column(pieces of mail) the second column(tally) will consist of how much mail you have. so for example let's say u got 3 pieces of mail that would go in the 0-4 category and then in the third column (frequency) you will write the number of tally marks for that category. example let's say your category is 0-4 and you got 3 pieces of mail. your tally mark would be three marks and your frequency would be the number 3 a histogram is basically a bar graph so the data that you get from the frequency chart will be in the graph
hopefully this help text me if you need any more help with this