You can add or change a payment method in Facebook (Meta) Ads Manager through the Billing section of your ad account. The exact steps can vary slightly depending on whether you're using a personal ad account or a Business Manager ad account.

Here is a general, step-by-step guide:

To Add a New Payment Method
Go to Ads Manager: Log in to your Facebook account and navigate to Ads Manager.

Tip: You can often find a direct link by searching "Ads Manager" on Google or navigating to facebook.com/adsmanager.

Access Billing: In the main Ads Manager menu (often located in the top-left corner under the "All Tools" icon, which looks like three horizontal lines or a waffle-grid), click on Billing.

Go to Payment Settings: On the Billing page, look for and click on Payment Settings (sometimes called Payment Methods).

Click "Add Payment Method": You will see a button to Add Payment Method. Click it.

If you are in a Business Manager, you might have the option to add a payment method at the Business Manager level first, which can then be assigned to ad accounts.

Enter Details:

A pop-up window will appear asking you to choose your location and currency (if not already set).

Select the payment method you want to add (e.g., Credit or Debit Card, PayPal, Online Banking, etc. - options vary by region).

Enter the required payment information (card number, expiration date, CVV, or log into your PayPal account).

Save/Continue: Click Next or Save to confirm and add the new payment method to your ad account.

To Change/Update an Existing Payment Method
You cannot directly "edit" or "update" the details of a credit card (like the number or expiry date). The process is usually to Add a new card and then Remove the old one.

Go to Payment Settings: Follow the steps above (Ads Manager > Billing > Payment Settings).

Add the New Method: Add your new or corrected payment method (e.g., the new credit card with the updated expiration date) by following steps 4-6 from the "To Add a New Payment Method" section.

Remove the Old Method:

On the Payment Settings page, find the old payment method you wish to remove.

Click on the three dots (...) or the Remove button next to the payment method.

Confirm the removal.

Important Considerations:
Admin Access: You must have admin access to the ad account or Business Manager to manage its payment methods.

Manual vs. Automatic Payments: Some ad accounts are set up for manual payments (prepaid, where you add funds to your account balance) and others for automatic payments (postpaid, where you are charged after you've accrued costs or hit a billing threshold). If your account uses manual payments, the process will involve adding funds rather than linking a card for automatic charging.

Business Manager vs. Ad Account:

Payment methods added to the Business Manager can often be used by multiple ad accounts within that Business Manager.

Payment methods added directly within the Ad Account's payment settings are specific to that one ad account.