After exploring underwater, the goblins find a way back to the castle.
Get Salt
Have 
Fingus click the swordfish's eye, then
have 
Winkle take the salt that
falls.
Get a File
Have Winkle stand to the right of the large pot to the
right of the swordfish.
Have Fingus click the cover of the pot, then
have Winkle use the salt on the fellow in the pot.
Then have Winkle click the small pots to the right of the
big pot. You will get a file.
Get a Thumbtack
Have Winkle stand near the rope in the top-left part of the
screen.
Have Fingus hold the rope on the right side of the screen,
then have Winkle pull on the rope on the left.
Have Fingus use the file on the chain on top of Colibrius's cage.
Then have Fingus click on the thumbtacks to take one.
Save the Game
The timing of the next part is difficult, and you will lose an item and have to get another if you don't do it correctly, so save the game to save yourself the trouble. If you don't do it correctly, you can just load the saved game to avoid having to get the item you lost.
Use Kind Elixir on a Meatball
Have Fingus stand behind the cook.
Have Winkle use salt on the meatballs, then immediately
go up to the shelf above
the cook so that he's just to the right of the light-colored step above the
cook. Then when the person looks through the window and complains about
the meatballs, have Fingus use a thumbtack on the case,
and when the meatball goes
flying, have Winkle use the kind elixir on the meatball.
If you miss, load the
save file if you made one, as recommended above. Otherwise, you will have to
get another thumbtack before you try again.
Go to the Throne Room
That's all you can do here right now, so move the cursor to the bottom-left of the screen until it turns into a door icon, and click to go to the throne room, or move the mouse to the top of the screen and choose the wooden sign, then click Throne to go to the Throne Room.