Hello Rahul,
After installing this plugin, enable it from the Joomla Administrator > Extensions > Plugins.
Now, go to Sellacious Backend > Settings > Payment Method, click on new and create a new method for PayTm.
You can submit your information which you got from the PayTm, in that payment method.
https://www.sellacious.com/documentation-v2#/learn/settings/payment-method
I hope this helps.
Thank You