This answer is simply pulling apart the quotation. If you control the present, you are able to present your version of the past because no one else is in control. Only you will be able to frame the past through your lens on history or the past. If you can control the past, that allows you to shape the future in your vision framed by what has happened in the past via your version. For example, if you see the laws governing pollution control as a good thing, you would present your view that the laws should continue so that the earth is not poisoned with pesticides or the chemical runoff of factories. If you see the laws as a bad thing, your vision of the future would be that the laws should allow businesses to do as they wish with waste products because that would be good for their businesses and thus good for the country. The laws would be considered government interference and thus up for change. The future would thus be much freer for businesses without the regulations controlling what they do. Now apply the same ideas to politics itself, and you can see that the quotation applies equally to the business of politics and the political party or people in control. They can slant news releases to support their versions of the future.