As long as you have a stepladder and perhaps a friend to help you unroll the batts and hold them in place, you should have no problem at all. Rolls need only be spread out across the entire extent of an uninsulated floor. If you live in a particularly extreme climate, or your house hasn't undergone serious insulation efforts in more than 20 years, you may want to consider taking actions that require a professional contractor. If you do decide to take such steps, shop around first. Not all contractors are equally skilled, and prices can vary widely.
Many people spend more on professional weatherization than they'll ever save on energy bills.
Both quality and price tend to be better. Make sure your contractor is licensed and insured. Most importantly, see what steps you yourself can take. You may find you can cut your energy bills down to size without calling in professional help. In fact, a small investment in time and money can have a handsome pay-off over the long term.