You can start by simply using excel. You can start by looking at your prior month spending and using that as a baseline for creating your budget. You can create categories to group your expenses into and decide how much you want to spend on those categories. At the end of each month you should go back and see how much you spent on those categories and see if you were able to stick to your budget. It may be hard at first, but if you hold yourself accountable, it will become easier with time.
If you want to make it even easier, their are great apps that you can use to help you. I like the app Mint which I link to my bank account.