Yes, you can post multiple images at once. To begin, go to Publishing and then either click View Calendar and click on any given day to schedule a post, click Schedule a Post to open the post scheduler, or simply click Compose at the top of your Dashboard. Select your content group, or choose to post without a content group, and you'll get to this screen:
Click Attach Media to start selecting the images you wnat to post to Facebook and/or Twitter, which then brings up this screen:
Also, please keep in mind that while you can add multiple images to a post, you cannot add more than a single GIF image to each post.