There are lots of different methods of meditation with lots of different objects you can use. Whatever method you use, it can be very helpful at the start of the sitting period to give yourself clear instructions that aren't lengthy and don't contradict each other. Repeat these instructions two or three times so the mind really understands what it is supposed to be doing. You can include in your instructions both what you are supposed to focus on and what you are not supposed to focus on.
eg. "I will be aware of the present moment. I will be aware of the present moment. I will be aware of the present moment. I will not give attention to thoughts of the past or the future. I will not give attention to thoughts of the past or the future. I will not give attention to thoughts of the past or the future. "
Then when the intention is clear simply let the mind get to work. Ajahn Brahm, who teaches this, uses the similie of a taxi driver. He says that if you give too many instructions and become a backseat driver then the taxi driver will throw you out of his cab. If you just sit in the cab and don't give any instructions then he won't know where to take you. Similarly, if you keep pushing and pulling the mind this way and that way the mind will get confused or "throw you out" of your meditation which can be very dangerous since it can cause a person to develop aversion towards meditation which should be one of the most beneficial things a person can do. If you don't give any instructions then the mind won't know what it's supposed to be doing. Give just the right amount of instructions and let the meditation progress by itself.
If after a few minutes you find the mind has wandered again simply repeat the instructions once or twice but try to be gentle and not too forceful.
Having established yourself in the present moment then you can give new instructions to focus on the breath, which is not a new object but is a more concentrated part of the present moment.
If you find this helpful I highly recommend getting yourself a copy of "Mindfulness, Bliss and Beyond" by Ajahn Brahm
which is one of the most comprehensive meditation manuals available and has cleared up a lot of my doubts and confusion as a beginner.