Breaking in new hiking boots takes time and planning. It’s not a big problem, though, so don’t be scared!
When you know you are going to need some new hiking boots, perhaps because you are going on a hike in the near future, plan ahead. Get your boots a week or two before the up and coming hike. When you buy the boots, be sure to try them on with a few different kinds of socks: the kinds you plan on wearing during the hike. Make sure they are not so snug they won’t allow your foot to expand some as you walk, but also they should not be too loose because of the danger of blisters.
When you have your boots, you want to make every effort to have them broken in before you start hiking. So wear them. Maybe wear them to work if you don’t walk too much. The point is that you need to use them for an hour or two each day, with the time increasing as you go along, in order to get your boots in shape for your hike.
A final word regarding care: try some waterproofing spray on your boots before you head out. Give them a couple of layers of the stuff, as this kind of care can greatly increase the life expectancy of your prized footwear.
Then enjoy your hiking!