Map out the necessary cable connections and pin outs.
You must be careful because there may be proprietary pin outs, cables, etc. involved.
You will need to reference the applicable User Guides/Manuals for the case, the motherboard, and the fans.
As well as for any other RGB lights that are installed.
= = = =
This case with the LED button being the second one up from the bottom?
https://www.1stplayer.com/productdetails/id/126.html
[Note: The User Manual link would not open at all for me.]