To use third-party tools, you need your FPL ID. Note: You should never enter your FPL password on any site other than Official FPL. Using your FPL ID, however, is perfectly safe.
To find your FPL ID:
Login to your account at https://fantasy.premierleague.com
Click on the Pick Team tab
On the right, there is a “Gameweek History” link – click it.
Once that page loads, check the URL in your browser address bar. The number in the URL is your ID.
Does having a low FPL ID do anything?
Yes, but not much. Its used as a tie-breaker for prizes.
As per Official FPL, if the two teams have the same amount of points then the winner is determined by who made fewer transfers.
However, if managers have the same number of points and transfers, only then will the FPL ID matter, in that the manager with the lower one will win the prize!