Radcoins are your account balance: not an item, can't be raided and kept across every wipe. You get them in the Tebex store, once for linking Discord (100 Radcoins), as a gift from friends, with voucher codes, referrals, the chat quiz or by trading in the Radcoin shop: 1.000 scrap = 1 Radcoin.
Trading: in the "Scrap → Radcoins" box you type the number of Radcoins you want and trade exactly that amount – or press "All" to trade as much as your scrap allows.
Spend them in the "Radcoin shop" tab (/coins or /radcoins): buffs for you, your team or your clan, the server-wide blessing, the premium season pass, items and packages. The sections are Highlights, Bought recently, Wishlist, Packages, Buffs, Items, Gift Radcoins and My history.
Every purchase first opens the "Confirm purchase" window with a preview ("What you get"), the price and notes such as discounts, daily limits or "already unlocked".
Wishlist, gifts, hourly deal, vouchers and history are explained in the article "Radcoin shop: wishlist, gifts & history".
Commands
/coins/radcoins