Auto subs

Can any1 please advice me on using the auto sub section, ive never used it as am normally available wen my matches take place but due 2 start work soon so mite not b about 2 watch the matches, do the subs only come on wen 1 of ur starting 11 picks up an injury, or will they come on at some point even wiv no injuries, and i see there r 2 spaces for each position, ie gk, df, wng, mid and fwd, do i put the player i want 2 come on and the player who he is gunna replace, help wud b much apreciated.

You place the replacements on their org. positions and the auto-sub option will be activated when a player of yours gets injured during the game (not tired or booked).

Auto subs only occur for injured players.