Retrieving passwords is not an option due to security measures. But since you are using phpmyadmin I suggest you do one of the following:
* Run this query:
update ost_staff set passwd = md5('yournewpassword') where username='admin';
* Change the password directly:
Replace the current password with 21232f297a57a5a743894a0e4a801fc3, this should set the password to admin