Hi. To add mysql database in the config, open the hue configuration file and search for the [[database]] section under the [librdbms] section. Then create a section [[[mysql]]] where you can add properties of MySql database. 
The properties you will have to add are:
# Name to show in the UI.      
## nice_name="My SQL DB"      
# For MySQL and PostgreSQL, name is the name of the database.      
# For Oracle, Name is instance of the Oracle server. For express edition      
# this is 'xe' by default.      
## name=mysqldb      
# Database backend to use. This can be:      
# 1. mysql      
# 2. postgresql      
# 3. oracle      
## engine=mysql      
# IP or hostname of the database to connect to.      
## host=localhost 
     
# Port the database server is listening to. Defaults are:      
# 1. MySQL: 3306      
# 2. PostgreSQL: 5432      
# 3. Oracle Express Edition: 1521      
## port=3306      
# Username to authenticate with when connecting to the database.      
## user=example     
 
# Password matching the username to authenticate with when      
# connecting to the database.      
## password=example