You always read a number from left to right. For example, 1,248 is read, "One thousand, two hundred and forty-eight." But when assigning place values, it's easier to start from the far right and work your way left. The first digit on the right always tells you how many ones are in the number. An 8 in that place means 8 ones are in the number.
As you increase the number of places in a number, each one represents a value 10 times the one to its right. The first place is ones. The second place is the "ten times one" place. Ten times 1 is 10, so the second place is the 10s place. A number with two places, such as 28, equals 2 tens and 8 ones. Two tens plus 8 ones equals 28.
To determine the value of each place as you add digits to the left, simply repeat the last place value and add a zero. Since the first place value is 1, adding a zero gets you the second place value, 10. To find the value of the third digit, add a zero to the second. The place value of the third digit is 100s. That rule applies no matter how big a number gets.
Using the number we started with, 1,248, and applying our "times 10" rule, it's easy to assign this number's place values and read it correctly. Starting at the right, there are eight 1's (8), four 10s (40), two 100s (200) and one 1,000s (1,000). Reading left to right, using our place values, this number (1,248) reads "one thousand, two hundred and forty-eight."