It is a great irony that when training, building muscle is something that women don't want and men do.
So while many women avoid resistance training, in the mistaken belief that they will get too big, many men are slaving away pursuing the Holy Grail of building muscle and building it fast! The reality is that building muscle in any quantity can be incredibly difficult. Many guys spend years working out without ever truly understanding what they need to do in order to get started.
The first thing to understand is that many people, and certainly the vast majority are women, are limited by their genetics. The spectacular size of professional bodybuilders seen on posters and in magazines is quite simply unattainable for the majority the population. However, if we assume that this is not your primary goal, then there are certain things that you can do to maximise the gains from your workouts. This is one area where taking advice from a professional trainer will do well worth your time and effort.
Successfully gaining size does not happen just by chance. It requires the right mix of workouts, rest intervals, and nutrition. There is no wonder combination that will work for everybody - you need to get a properly designed programme that takes into account your exercise history, your health, your goals, and the time have available to work out.
If you get all those things right, you can expect to see a reasonable increase in size as a reward for your efforts. But it is worth noting that this is not a short-term project - everybody goes through a series of growth periods and plateaus, so having the right mental attitude can be as important as anything else.