Okay, so if I were you, I would google "making gifs with ibisPaint". If you already know kind of how to animate in the program, it's probably just a matter of saving it the correct way. But by googling that, if there's a similar app that can convert the animation to gif, it will probably come up.
Once it's saved in gif format, it is the same process as uploading a regular comic page on tapas.
This is what comes up on youtube:
https://www.youtube.com/results?search_query=how+to+make+gif+animation+ibispaint
Keep in mind tapas is not a site for animation. Anything animated will probably need to be on the smaller side. Just something to be mindful of!