Put the plugin file into you plugin folder and restart the server so that the plugin can generate the new config settings.
Set the Type setting under Repository to MySQL
If you have an old pets.db file you want to import set ConvertFrom setting under Repository to SQLite(or what Type was before).
create a new database (collation: utf8_general_ci) on your MySQL server (default: mypet).
replace the credentials under MySQL with your own.
restart the server once again. It should create the tables and import the local file to the database.
OPTIONAL:If you want to merge multiple pets.db files into one database you can use the script at the bottom of this page.
You can run your server like normal but all servers you use can now access the pets from one database!
MySQL Merge Script
If you want to merge two MyPet databases, they need to be on the same server and have different names. Just download the file in the spoiler and fill in the correct credentials and database names and the PHP script will merge them together. Different (MyPet) owner UUIDs are no problem as long as the player name or the Mojang UUID are the same.
Please make backups of your databases before you try to merge them!