Save the animated GIF to your device
Convert the GIF to a video format if needed
Open Instagram
Tap the plus icon to create a new post
Select the converted video or GIF-compatible file
Edit the post if desired
Add a caption and hashtags if needed
Tap Share to post it
Use Instagram Stories if you want to upload a GIF-like animation more easily
Use a third-party app if Instagram does not accept the GIF directly