If you have already advertised with Facebook using your Current account, Facebook will not allow you to add money to this account.

To add money to Facebook account and pay for boost or advertising, you should:

• create a New account
• assign Page Admin role to this New account
• add money to this New account Available balance
• use Available balance to pay for boost or advertising

To complete all these steps please check the manual below:

• Create a New account on Facebook with your real information: first name, last name, contact number, birthday
  
• Upload your real photo to your New account to avoid any problems with Facebook
• Log Out from your New account
• Log In to your Current account
• Open your Page and click Settings
  
• Click Page Roles
  
• Under Assign a New Page Role text type in your New account name, select Admin, click Add
  
• Log Out from your Current account
• Log In to your New account, click Accept to become an admin of your Page
  
• Follow this manual