To run ads on Instagram using your Facebook Ad Account, you'll primarily use Meta Business Manager (formerly Facebook Business Manager). This centralized platform allows you to manage all your Meta assets – Facebook Pages, Instagram accounts, Ad Accounts, Pixels, etc. – in one place.

Here's a step-by-step guide:

Prerequisites:
Before you start, make sure you have:

A Facebook Business Page: Your Instagram Business Account must be linked to a Facebook Page.

An Instagram Professional Account (Business or Creator): Personal Instagram accounts cannot be used for advertising in Business Manager. If you have a personal account, you'll need to convert it to a professional account (you can do this in the Instagram app's settings under "Account" > "Switch Account Type").

A Meta Business Manager Account: If you don't have one, go to business.facebook.com and follow the prompts to create one.

Admin Access: You need admin access to your Business Manager, the Facebook Page, and the Instagram Professional Account you wish to link.

A Facebook Ad Account: This is where you'll manage your campaigns and where your billing information is stored.

Step-by-Step Guide to Link Your Facebook Ad Account to Instagram (Using Business Manager):
Part 1: Link Your Instagram Account to Your Facebook Page (If not already done)

This is often done directly within the Instagram app or Facebook Page settings, but it's a foundational step for advertising.

From your Instagram App:

Go to your Instagram profile.

Tap the Menu icon (three lines) in the top right.

Tap Settings and privacy > Business tools and controls (or Creator tools and controls).

Tap Connect a Facebook Page (or Page if already connected).

Follow the prompts to select an existing Facebook Page or create a new one.

From your Facebook Page (New Pages Experience):

Go to your Facebook Page.

Click Manage Page (or similar button to access professional dashboard).

Look for Linked Accounts or Page Access & Settings.

Find the Instagram option.

Click Connect Account and follow the prompts to log in to your Instagram account and link it.

Part 2: Add Your Instagram Account to Meta Business Manager

This is where you bring your Instagram account into your centralized Business Manager.

Go to Meta Business Manager:

Log in at business.facebook.com.

In the left-hand navigation, click Business settings (the gear icon).

Navigate to Instagram Accounts:

In the Business Settings menu, under Accounts, click on Instagram accounts.

Add Your Instagram Account:

Click the Add button.

A pop-up will appear. Choose Connect your Instagram account.

Enter your Instagram account's username and password and click Log In.

Follow any on-screen prompts to confirm the connection and grant necessary permissions.

Once successful, your Instagram account will appear in the list under "Instagram Accounts" in Business Manager.

Part 3: Assign Your Ad Account to the Instagram Account

Now that your Instagram is in Business Manager, you need to tell it which Ad Accounts are allowed to use it for advertising.

Select Your Instagram Account:

While still in Business settings > Instagram accounts, click on the Instagram account you just added (or want to link).

Assign Ad Accounts:

In the panel that opens on the right, click the Connected Assets tab.

Click Add Assets.

In the pop-up, select the Ad Accounts you want to link to this Instagram account. Check the box next to each relevant ad account.

Click Add.

Part 4: Verify the Connection (and what to do next)

Check in Ads Manager:

Go to Meta Ads Manager (you can access it from the Business Manager dashboard or directly at facebook.com/adsmanager).

When creating a new campaign and setting up your ad set, under the "Placements" section, choose Manual Placements.

You should now see the option to select Instagram Feed, Instagram Stories, Instagram Reels, etc., and your connected Instagram account should be available as the identity for your ads.

Troubleshooting Tips:

Permissions: Ensure you have admin access to all connected assets (Business Manager, Facebook Page, Instagram Account, Ad Account).

Instagram Account Type: Double-check that your Instagram account is a Business or Creator account, not a personal one.

Clear Cache/Cookies: Sometimes a simple browser cache clear can resolve minor display issues.

Refresh Connections: In Business Settings, sometimes refreshing connections or re-adding an account can help.

Facebook Help Center: If you encounter persistent issues, Meta's (Facebook's) Business Help Center is a good resource.

By following these steps, your Facebook Ad Account will be properly linked to your Instagram account within Business Manager, allowing you to seamlessly run ads across both Facebook and Instagram using the powerful targeting and optimization capabilities of Meta Ads Manager.