Go to IWD OPC-IWD Agency-One Page Checkout

Enable one page checkout - Enables/Disables IWD One Page Checkout module
Show Login Form - Enables/Disables login form on a checkout page
Show Order Notes Field - Enables/Disables order notes on a checkout page
Show discount form - Enables/Disables discount form on a checkout page

One Page Checkout by IWD agency divides the checkout into 3 separate columns for better user experience - Billing Address, Shipping Method, Payment Method.
Fill in the required columns and press Place Order button
If you choose one of the following PayPal Payment buttons you will have to login in your PayPal account

After you logged in the system will offer you to choose payment option

After clicking Continue you will be redirected to the checkout with all of your required information fields already filled in based on the information on your PayPal account
 
Checkout with virtual product
When user proceeds to checkout with virtual product they see only two columns (shipping method is not included in checkout process automatically in that case)