Step 1. Count the number of repeating digits.
Step 2. Multiply the number by 10 to that power.
Step 3. From that product, subtract the original number.
Step 4. Divide the result by 1 less than the multiplier of Step 2.
Step 5, Reduce the fraction.
For your number

Step 1. There are 3 repeating digits
Step 2. The multiplier is

. The multiplied number is

Step 3. Subtract the original number

Step 4. Divide by 1000 - 1 = 999

This fraction does not reduce, so you are done.