Considering that Hugtto's a thing, it's honestly wierd seeing the Kira Kira Precure A La Mode background when the new series has been out for about a few episodes, so I'm asking you to maybe update the background in honor of the new season please! XD
No no, don't worry about that! adding information to an infobox is not always easy and can be quite confusing. I've made this help a while ago: Fairy Tutorial: How to add pictures to Templates however, this one seems a little outdated since it only explains it for the non-portable infoboxes.
If you use the old ones (usually used here), you can follow this tutorial, however, if you do use the portable ones - and edit via visual editor - you can just click at the infobox and edit it, then, you should have the option to upload a image right into your infobox.
I hope this is somehow helping you. If not, I'd make some explaining screenshots for you ~ But I can only explain it for computer users, hehe. If you use the phone, you might have to ask those who edit via phone as well.