First upload files you want to add.
Then open your character page -> Cards
Click 'Edit'
Where you have that 3 dots (right side, up), click on Visual Editor and choose Source editing.
Then go down and see files names, like:
File:2nd_Anniv_Ichirou.jpg|2nd Anniversary
File:2nd_Anniv_(evolved)_Ichirou.jpg|2nd Anniversary <small>(evolved)</small>
Just do Enter and write/paste Flie:[Name] (without [] )
Like File:(My_hood)_Dice_Arisugawa.jpeg
You can copy it from your uploaded file's page
http://hypnosis-mic.fandom.com/wiki/File:(My_hood)_Dice_Arisugawa.jpeg
If you add | you can type the card name, like My hood
If you add at the end <small>(evolved)</small> you'll get small font for evolved.
You can check Preview to see your changes if you want.
To be honest I just learnt how to do this myself :D So complicated, because the gallery do ont show my cards :D
This nice person showed me screenshots, if you want to see~
https://hypnosis-mic.fandom.com/wiki/Message_Wall:KannonzakaDepression