Authors must visit the abstract page via the list of papers. The abstract page looks like this:
In the right side nav bar, you can see a module named ‘Proceed to Payment’. The following image will make it clear for you.
Once you click on the ‘Proceed to Payment’ button, you shall be led to a page similar to the one shown below.
If you want to make a direct payment to our bank account rather than using PayPal, then you can click on the ‘Don’t have PayPal?’ link. It will lead you to a page similar to what is shown below.