If you have the Oracle MySQL version of ExSync then configuration options are:-
MySQL Server connection is set from within ExReport once the MySQL Server Schema has been installed.
The MySQL connection string dialogue is accessed from the main application toolbar

A dialogue appears:

Add the MySQL host name to the 'Server Name' Field:

Then add the MySQL port the default is 3306:

Then add the root admin user name and password:

Finally select the MYSQL database the default schema that ships with ExSync is Exch_SQL:

Save the settings.