When in examine-mode you can setup a board position with this command. FENstring is the FEN-representation of the Board. sidetomove is either "w" for white or "b" for black to move next
FENstring:
The board contents are specified starting with the eighth rank and ending with the first rank. For each rank, the squares are specified from file a to file h. White pieces are identified by uppercase piece letters ("PNBRQK") and black pieces are identified by lowercase piece letters ("pnbrqk"). Empty squares are represented by the digits one through eight; the digit used represents the count of contiguous empty squares along a rank. A solidus character "/" is used to separate data of adjacent ranks.
eg. The standard-board looks like this:
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR
The Wild 5 - board looks like this:
RNBKQBNR/PPPPPPPP/8/8/8/8/pppppppp/rnbkqbnr
The Position (Ruy Lopez-opening)
W: P a2 b2 c2 d2 e4 f2 g2 h2 R a1 h1 N b1 f3 B c1 b5 Q d1 K e1
B: P a6 b7 c7 d7 e5 f7 g7 h7 R a8 h8 N c6 g8 B c8 f8 Q d8 K e8
is represented by
r1bqkbnr/1ppp1ppp/p1n5/1B2p3/4P3/5N2/PPPP1PPP/RNBQK2R
See also: examine