The main thing is that except for the setup, Chess960 is
just chess. The difference is that the major pieces are
positioned mostly randomly, but with two constraints.
The king is always positioned between the two rooks.
The bishops are always placed on opposite colors.
some method of counting, there are 960 possible opening positions.
Hence the name. Consequently, there is no opening book; but
all the chess principles you know from standard chess still apply.
Check/Checkmate, forks, pins, mobility, doubled pawns; everything
you know or ought to know about chess still applies - except you can't memorize openings.
Castling: Is simple; the "kings side" and "queen's side" castling moves end with the king and rook in the same positions as in standard chess, regardless of their starting positions. On Boardspace, you indicate castling by moving as though the king were going to capture the rook.