if you want to use Cashfree in Nexelit cms, At first you need to get your client id and client secrets , you have to setup your Cashfree gateway settings. Go to “General settings>Payment Gateway Settings > Cashfree settings”.
Go to Cashfree.com login to your dashboard. then click on Payment Gateway > Try Environment button.
you will find option to go to production mode in top right corner a button name Switch to Production
now click on developer > api
the process is same for production mode.
make sure you have whitelist your domain, it is new requirements from the cashfree in their latest version of api update follow this url for more info https://docs.cashfree.com/docs/developers-whitelisting