This article explains three ways to send a photo from your iPad to Facebook.
Share photos, videos and more from your iPad to Facebook
There are two ways to use the Photos app to send images to Facebook. One is for images you've previously taken, and the other is for an image or video you've just captured with the Camera app.
To use the Photos app, open the app and select the image you want to post to Facebook. If you want to send multiple at once, choose Select and then tap each photo or video you want to post to Facebook.
To send a photo or video you just took, stay in the Camera app and tap the thumbnail of the image or video.