(This information is taken directly from Facebook’s Help Services)

Before you begin

Create a Custom Audience from a customer file

Get Started
To get started creating a Custom Audience from your customer file:

From there, there are five parts to creating your Custom Audience:

Below, we’ll breakdown each one.

Add Customer File

To add a customer file:

Tip: You can download a data file template we’ve created that’s set up to help our system map your data more easily. Click Download file template to check it out.

Edit Data Mapping
We show you a preview of your data and how we’d classified it. There are three statuses you may see in this preview:

means we think we know what type of data this is (but you can correct us if we’re wrong – see below) and will use it when trying to match the information in your customer file to people on Facebook. Only the data with this symbol gets uploaded for matching.
means we’re not sure what type of data this is or you’ve told us to leave it out of matching. If we’re not sure, you can tell us (see below). Check out our best practices guide to make sure it’s formatted in a way we can use.
means the data type has been identified (either by us automatically or by you), but we can’t detect a supported format. You may have to reformat the data in your file or select a formatting option from a Choose format dropdown (see below). For example, birthdays can be listed in different formats like MM/DD/YYYY or DD-MM-YYYY. Learn more. You can also leave the data type out of matching (see below).

Note: If you’re seeing a lot of errors, it may be because we’re looking for the wrong delimiter (the punctuation mark that separates data points). You can change this by hovering over “modify the delimiter” and choosing a new one.

You can interact with your data preview in three ways:

To change your data’s type, click the dropdown and choose what type of data you’ve provided. From this dropdown, you can also choose Do Not Upload, which tells us not to use that data when matching.

To change your data’s format, click the Choose format dropdown and choose what format we should be using to match your data.

Note: Every piece of data requires a type to be usable, but only some kinds require formatting details. You’ll only see the Choose format dropdown if it’s necessary.

If you need to change anything about your customer file to maximize the number of identifiers we can use, do so now. Once you’re ready, repeat the steps above. When you’re satisfied, click Create & Upload.

Hashed Upload & Creation
We hash your data, upload it and create your audience for you. This may take a little while if your file is large. Feel free to continue working in another browser tab or window while you wait.

Next Steps
When we’re done creating your Custom Audience, we automatically generate a list of next steps you can take to get the most out of it. You can take one of those next steps immediately or click Done to finish.