Action Details
Requirements and how-to articles for Facebook's action:

paid action
Create a carousel ad to appear in users' News Feeds.

You need this to get it done:

A unique headline for each image/video in the carousel (up to 25 characters each.)
A short description to accompany your ad (maximum of 90 characters.)
Carousel Images
Between 2 and 10 images (if not using videos.)
File format: .jpg/.jpeg or .png
Maximum file size: 30MB
Ratio: Recommended 1:1
Resolution: Recommended at least 1080 x 1080 pixels
Carousel Videos
Between 2 and 10 videos (if not using images.)
File format: Recommended .mp4 or .mov (but most formats supported)
Maximum file size: 4GB
Maximum video length: 240 minutes
The link you wish to include in your post (where you would like to send your audience to.)
Choose what call-to-action button you want underneath each image/video.
Target Audience
Decide on the audience you want your post to reach (gender, age, location, interests, etc.)
Duration and Budget
Choose how long you want your ad to run and what your daily budget is.
Choose currency, enter payment details and pay.
Requirements missing or found errors? Report

How-To Articles
A list of useful links for you:

Facebook Ads Guide - Carousel (Facebook feed)
Specifications and requirements.
Facebook Ads Help Centre - About the carousel format
About carousel ads (benefits, specifications, insight reports, etc.)
Facebook Carousel Ads
Information about carousel ads - when and how to use them.
Link missing here or found errors? Improve How-Tos