Locate Pixels in Ads Manager
First, navigate to Facebook Ads Manager by clicking here.
Once inside Facebook Ads Manager, first double check you have the correct ad account selected. You'll want to select the ad account that you'll primarily be using for your campaigns.
Since pixels are unique to an ad account, you'll always want to verify that you've selected the right ad account before grabbing your existing pixel ID or creating a new one.
Once the correct ad account is selected, click near the top left to expand the dropdown menu. Click on "Pixels" under the Measure & Report column.
Your Pixel ID should be listed right underneath the name of your pixel if you've previously created one. You can easily copy and paste this pixel ID for self-serve installation.
Creating a New Facebook Pixel
If you haven't previously created a Facebook Pixel, either click "Create a Pixel" towards the bottom or "+Add New Data Source" -> "Facebook Pixel" on the left to create one.
If you're creating a new pixel, double check that you're creating it in the correct ad account.
First, choose a name for your pixel (you can always change this later). Then enter your website URL for your pixel if you wish to.
After creating your pixel, you can exit out of the setup window. You'll then be able to find the ID of your newly created pixel to copy into any self serve pixel installation tool.