I'm new, first I create a mysql database, but how do I use the phpmyadmin, cause I'm not sure my login username and password is equal to database username or something?

I really appreciate for your kindly help!

Use your websitename_database username.

Ex. if your website is named "mywebbie.vndv.com" and your database username that you've created is "webbie," your login would be "mywebbie_webbie"

Your password would be the password that you've created.