Copy the files from this plugin into the corresponding folders on your installation, as mentioned below:
- Copy the Paytm/gateways/paytm.php file into your installation's /module/gateways/ folder
- Copy the Paytm/gateways/callback/paytm.php file into your installation's /module/gateways/callback folder.
- Copy the Paytm/gateways/paytm-sdk folder into your /module/gateways folder