This section covers you on how to setup the PayPal as your payment gateway. I use our PayPal Sandbox login as example.
Step 1: Since we are using PayPal Sand Box we should have an account in http://developer.paypal.com. Login and click on the API Credentials to get the configuration values.

In case of live login to
www.paypal.com and navigate to Profile -> API Access -> Request API Credentials and choose Request API Signature and click submit. You case get the values from there.
Step 2: Configure these values in SMS Parameters. Login to your Joomla website as Super Administrator and go to JEEMA SMS control panel. You can see “Parameters” icon at the right side. Click on that and navigate to “Package Options” and provide the above 3 values in the respective boxes and click Save. Make sure you choose the right “PayPal Type”
Step 3: Create SMS Packages and create a menu link for SMS Packages view. So, front-end users can click on that menu link to see what all the packages available for purchase.
Front-end users can see a “Buy Now” link at the right bottom of every SMS package. They have to click the “Buy Now” link to start the payment process. Note only registered members can buy the SMS packages.

Verify the package details and click the “Buy Now” button. Once the buy now button is clicked it will take you to the PayPal website and ask the customer to login.

The customer has to give his PayPal login details to login. If you are using the PayPal sandbox give the _per account and login.
Once login is success PayPal will ask the customer to review the order and click “Continue” to continue

Once the “Continue” button is clicked it will come back to your
Joomla website and ask the customer to review the complete details and click
“PayNow” to complete the payment. Once the
“PayNow” button is clicked then the transaction is complete.
You will get the below message in case of success.

Customer can see their invoices under “Invoices” view.
Note: Once the customer complete the payment a valid SMS account will be created for him to access.