To add a bonus code to your deposit you will have to enter it after you enter your payment information. Please note: The process is different via PayNearMe - you can see that process here.
Step One: When on the home page click on the cashier.
Step Two: Click Deposit on the drop down menu.
Step 3: Choose your preferred deposit method on the left hand side (in this example we chose credit/debit cards), enter your payment information, and then enter the bonus code in the bonus code field shown by the red arrow below.