If you take suppose 289 as the number. To find the square root it should be done in pairs of the numbers. Start the pairing from the right hand side of the particular number . In the case of 289, the pair will be one pair is 89 and the other pair is 2.
The divide the first pair from left side of the number. Divide with a number which fully divides 2. Because, there is no number so we take a number which is less than 2 which is 1. So in the quotient write 1 and then 1 to the divisor which comes as 2. So, after 2 add a number which when divided by 2 and the number the answer comes.
(If you did not understand see the file)