How do you do long division?

Very difficultly.  No, really, it's not difficult.  It's a pattern.  Once you find the pattern, it's easy.  It is hard to describe in words.  So, I have a problem worked out for you as I describe it.First, the problem we will do is 79 "divided by" 3.  Notice the setup.  That's one thing students do incorrect a lot.  The first number goes inside; the second goes outside.So, now, remember, it's a pattern.  There's about 5-7 steps to it.  So, be patient, especially at the start.
You start to go through the numbers one by one.  What I mean is, "How many times does 3 go into 7?"  If the answer was none, you would "include" the next number (here, 79).  But, for us, 3 goes into 7 twice.  So, 2 goes above the 7.
Then, do 3 times that number you found, 2.  3*2 = 6.  That goes under the 7.
Then, you do 7-6 = 1.  Put the 1 underneath all, just like a subtraction problem.
Then, you drop the next number that is "inside" the long division symbol.  For us, that's the "9".  So, you write the 9 beside the 1, giving "19".  As it looks, the "9" dropped straight down beside the 1.Then, you repeat these steps.  As in. . ."How many times does 3 go into 19?"  That is 6.  So, 6 goes above the 9, next to the 2 that is above the 7, on top, giving us "26" on top.Then, 3 times that number, 6, = 18.  Put that under the 19, then subtract those two numbers.  19-18 = 1.There are no other numbers to drop.  So, 1 is considered our "remainder".  So, on top, after the 26, we would put "r1".  So, our entire answer would be "26 r1".Hopefully not making things more complicated, depending where you are in your math, you may or may not need to know this yet.  You will get it at some point in time.  I will try to keep it simple.  If you are looking for a "decimal" for your answer, you would repeat these steps still.  "But, what number do I drop?"  You would drop "0".  Keep dropping "0", until you get a remainder of "0", or you start to get a pattern, or you are told to stop.If you need a fraction for your answer, you have the "26".  We need a fraction after that, a top number and bottom number.  The top number is the remainder always; here "1".  The bottom number is always the "outside number" at the beginning here, "3".  So, the fraction would be 1/3, and the answer would be "26  1/3".