You can do this either manually or directly. We know that whatsapp backup’s data at 4 am every-day and stores them to your SD card. So, you can directly restore your deleted messages once you reinstall the application. When you do this you are prompted with restore chat history and you need to select restore. That’s it your messages will be restored from the backup file. Just read this post How To Recover your deleted Whatsapp messages – Directly
Restore your deleted Whatsapp messages
*.Go to file manager then SD card and then go to Whatsapp database folder.
*.Here you can see some file names in the format: msgstore-yyyy-mm-dd.1.db.crypt. Similarly, you can also observe a file named as msgstore.db.crypt (rename this file by adding anything before or after it).
*.After renaming it, select the file with date that consist of message that you have deleted accidentally.
*.Now rename the selected file to msgstore.db.crypt.
*.Finally, go to settings then application then to manage application and then go to Whatsapp and click on clear data.
*.Now run your Whatsapp and select restore and your file saved as msgstore.db.crypt will be restored.