What is my Stack Exchange account id?
Click on this link, you will be redirected to your Stack Exchange account page.
Copy and paste the URL of this page in the URL of your Stack Exchange Account field, then press Add.
Or
Enter the value manually in the Stack Exchange Account Id field:
Your account ID is in the URL (displayed in the address bar) as https://stackexchange.com/users/[Stack Exchange Account ID]/Your username.
Copy and paste your account ID in the form above, then press Add.