Note: 
Backup your files and database before upgrade.

Updation Steps:

1) Connect to your hosting server.
(Use your hosting control panel "File Manager" application or connect using FTP access)

2) Go to script installed location. 

3) Unpack downloaded ZIP package file and go to below directory:
"/Upgrade/v3.3 to v3.4/Upload/"

4) Now upload all files present at "Upload" directory into your server and overwrite existing files.

5) Execute "upgrade.php" file.

Example:
https://your-website.com/upgrade.php

You have done the work!