Hi Anbu,
The normal pattern is to make HTTP GET request to the local token service from your code running on App Services. The response will give you the token you need to connect to the service (in this case Azure Database for MySQL Flexible Server). Please see article below:
Based on what is written in below article you would use the access token you retrieved above as the password when connecting to the database:
Please click Accept Answer if the above was helpful. If something I wrote above is unclear or you need additional assistance please add a comment below.
Thanks.
-TP