Navigate to: FIFA 16\data\db\fifa_ng_db.db If you don't see a data folder, you need to use File Master to unpack the Data_Graphic.big file first.
Copy fifa_ng_db.db to your desktop. Never edit the original without a backup.
Download the editor, backup your files, and start creating. Your ultimate FIFA 16 career mode is just a database edit away. Modifying game files can result in crashes or online bans. FIFA 16 online functionality is largely deprecated, but we recommend disconnecting from the EA servers while using edited databases. Always play career mode offline after applying DB edits.