If you have a pokemon that you wish to sell in the forum (such as a shiny, in this case), post it in the relevant section, with your asking price. If you want to run an auction on your pokemon, include a few of the basics: A warm introduction, the starting bid (the price that you want to open the bidding at, such as 50k...someone may say "start" to start it off), a min bid (the minimum that someone has to bid after start), forms of payment (most commonly pokedollars), the duration of the auction (24 hours / 48 hours or whatever after the first bid). Do some reading, and observe other accounts running auctions, to get a feel for how it goes. If you don't feel confident enough to run an auction, I'd suggest simply listing your pokemon with a price and wait
https://pokemonrevolution.net/forum/topic/29538-forums-and-in-game-general-trade-rules/