All good advice above. It's also worth pointing out that when trying to build muscle you cannot do the whole day in one go so by splitting body parts out you can train each day if you want, you should have at least one day rest a week though. Traditional splits are, for example:
Day 1 Chest/triceps
Day 2 Back/biceps
Day 3 Shoulders/traps
Day 4 Legs
Note you should aways do the big muscle groups first, so on day 1 for example do the chest first then the triceps. Note that the above can be cycled indefinately because there is at least 3 days rest between each. Also it's good idea to do at least 20mins cardio and some ab work each session. Good luck