Once you've obtained the Lucky Coins and Dragon's Eyes have them in your inventory (see B68WW's reply for how to get them), type /level, and click on the green glass pane.
For reference, the Ice Dragon, Goblin, Bear, and Seamonster bosses spawn in the Bossworld's Bronze zone. The drop rate for boss-specific drops (Lucky Coins, Dragon's Eyes, etc.) are pretty rare, so if you don't get any from killing a boss or being in the Top 10 just try again later.