I've never done one in Canva, but it looks like the option is after you create the series of images, click Download and select .gif (beta). It's fairly rudimentary and just goes through the different pages you had for the project. It looks like with a Pro Canva account they do have a new Animator tool which has more options.
If you are able to get an .mp4 video, just google "mp4 to animated gif" and you'll find several sites that will convert. The one time I made one I simply used Google Presentation, created a series of slides and then use a program to screen capture and create a video as I moved through them. Then I converted the mp4 video to an animated .gif. I was using a system named VidGrid which my school licenses for both the screen recording and the conversion to .gif, but there are other free tools available. Below is my silly example I made with that technique.

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