Single post in Site Skins: How-To, and Helpful CSS

Hey, I need some help with the alert for shinies etc. in the shelter. I use Chrome on an iPad, and I have absolutely no clue where I need to even put the code. Do I put it in my about? Somewhere in my browser settings? The OP (Original Post) does not specify this. I've looked through a few pages, but I haven't found anything, and I am definitely NOT going through (at this time) all 222 pages. ...Help?