Keep t in internal storage under whatsapp /databases folder. When u install whatsapp and after putting in your number, it will ask if you want to restore
Press restore. It will work
Titanium Backup is the best to backup Whatsapp data, if you're installing new whatsapp and if backup data file above 20 mb, it almost takes around 3 or more time to restore, restoring from Titanium Backup is like bookmark backup.