Macbeth decides exactly what he will do at this point, ie. stand and fight. A resolution is a decision, and "pull in" gives an image of (for example) pulling in a net full of fish. So now he gathers his resources and acts.
The doubt fdmaxey mentions is about the prediction of Birnham wood having a confusing or hidden meaning - Macbeth now realises the unimaginable (Birnham wood moving to Dunsinane) has happened exactly as predicted... the prediction was neither a lie nor a riddle (=equivocation).
People don't speak like this nowadays. You could say it as a quote (meaning "Ok, enough messing about, time for a decision"), but I think even hardcore Shakespeare fans would miss the reference.