Just asking this question is your first step! There are a lot of students who would not ask this ever.
First, you have to study in a place and at a time with no distractions, or at least the right kind of distractions. More than anything else, this is critical.
Bad ideas: study where brothers and sisters or friends are playing, studying where it's too cold or hot, studying when you are too sleepy.
Second, you have to find out what motivates you in your setting. Some people find that listening to the right kind of music helps them study. Others find that having a lot of blank paper around to jot notes on, or doodle on, helps. Yet others find the just having a single scented candle burning in front of them helps. Bottom line: You have to figure our what you need around you that calms you down, allows you to focus. Everybody is different.
Another thing that helps is having a goal, and fully believing that your studies are taking you towards that goal. Say to yourself, "if I study, I will be able to ..." and fill in the blank. Write down that goal and keep in in sight at all times.
Last piece of advice: Don't think that you will have to study forever. Set a limit. For example, "I will study for 60 minutes; I can do that. After 60 minutes I can do something else." You may decide, after 60 minutes, to continue studying. If so, set a new time period. If you limit the commitment, the task doesn't seem so impossible. Take it one hour, or one half hour, at a time.