This code can be inputted in the Source editor. To access Source Editor, click 'Classic Editor' near the title of the page then to the 'source' tab. Down below is the code format of the spoiler box:
{| class="mw-collapsible mw-collapsed wikitable"
! <span style="color:pink;">Warning</span>: This tab contain spoilers from the Korean Version of ''Abide in the Wind''
|-
|>Text and info here<
|}
Result:
| Warning: This tab contain spoilers from the Korean Version of Abide in the Wind |
|---|
| >Text and info here< |
To change the color of the word 'Warning', replace the word 'pink' to the color of your choice.
To add information and or images, replace '>Text and info here<' with the desired text.