How do you swap postion of the castle and king when they are next to each other?

http://www.chess.com/learn-how-to-play-chess.html#special

Are you asking about castling?  Unless you are speaking about chess960, you cannot castle when the king and rook (castle) are next to each other because that means that one or the other has already moved, and you can't castle under these circumstances. 

The "castle" you're talking about is actually called a ROOK. "Castling" is a special move involving your King and one of your Rooks. Castling can be done to either side of the board, left or right - but we refer to that as "Queenside" or "Kingside" castling. Most players prefer to castle quickly in their games, me being one of them.

I don't know if you're aware of the special rules involved with castling, but in case you do not, I'll explain them for you: You may NOT castle anymore if either your Rook or King has already moved, even if you move them back to their starting square. You may NOT castle if your King is in check. You may NOT castle if your own or your opponent's pieces are blocking the way. You may also NOT castle if your King moves THROUGH check during the castling.

So, remember: the "castle" is not a piece, it is a special move for the King and the Rook. What you called the "castle" is a ROOK. I must say, I'm truly surprised that you don't even know the names of the chess pieces...

Thanks for the advice. How do i actually do it though? Do i just drag the ROOK onto the position of my king, because i keep trying to do it and nothing happens. I've only been playing for three weeks by the way.

Drag your king two spaces towards whichever side you want to castle.