There are a few ways that you can monetize your Facebook page – In-stream ads, Fan subscriptions, and Brand collaborations.

Facebook pages must have at least 10,000 followers, and must generate at least 30,000 1-minute views on videos that are at least three minutes long in the last 60 days to be eligible for monetization.

In-stream ads will play relevant advertisements before, during or after your video. This type of monetization is great for creators who make longer videos and content that is suitable for advertisers.
To apply for this, you must ensure that you’ve met the initial requirements (10,000 followers, 30,000 1-minute views), then you can apply directly via the creator studio by heading to the monetization section.

Fan subscriptions is ideal for creators with a large, active following. It allows fans to directly fund your page through monthly payments. Fans are identifiable by a special badge, and are rewarded with perks like exclusive content and discounts. This model is currently only available by invitation from Facebook.

To monetize with Brand collaborations, you don’t have to meet the initial requirements, but you must have 1,000 followers and one of the following: 15,000 post engagements, or 180,000 minutes viewed, or 30,000 1-minute views of 3-minute videos in the last 60 days.
You can then request access to the branded content tool, and then apply directly to brand collaborations.
This is perfect for pages with an active, loyal following, and content most brands won’t see as too risky.

With each type of monetization, you must ensure that you’re adhering to Facebook’s Community Standards, Payment Terms,  Page Terms, Content Monetization Policies, and Content Monetization Terms.