You can install a bathtub on with the correct tools and a little help. There are plenty of tutorials available on the Internet for how to install a bathtub, but here is a general overview of what the task involves.
Start by removing as much as you can from the bathroom. You want a clear space in which to work. Once this is done you will be removing the old bathtub and then insert the new one.
This task will take about two days, and you need someone to help you with lifting both tubs out and in. After you remove the items from the bathroom turn off the main water valve. Remove the hardware and faucet from the tub.
You should already have the new tub ready to fit exactly into the drain and spouts. If not, you will need to get another new bathtub. Take out the drywall from about two feet above either end of the bathtub.
Next, use a utility knife to cut any dried silicone away. Remove all flange screws. Now, get your partner to help you pull the bathtub out. Next, install the new bathtub by reversing these steps.
Once the bathtub has been installed in between the walls, check that it is even using a level. Put the level on the edge of the top of the tub and not the bottom. The tub bottoms are usually sloped to allow for draining so do not check for leveling there.
This is the basic overview for how to install a bathtub. As you can see, it is relatively easy to do with the help of a friend and the right tools. Get exact details from someone at your home improvement plumbing department or from videos or articles online.