Pay Pal & WordPress Integration

This is a total newbie question I realize but how do I make sure that when I use a Pay Pal button on my WordPress site that payment will go to my Pay Pal account? How is the button associated with my Pay Pal account inside of WordPress is my question. Should I be sandbox testing payments before going live? I have a really simple registration form and one click payment I just want to get all of the Pay Pal information correct before going live. Any and all help very appreciated. I am new to e-commerce and just want to understand the relationship between the plugin and my pay pal account a bit better.

https://wordpress.org/plugins/wordpress-simple-paypal-shopping-cart/