Which watch and which bracelet?

You can look up tutorials online (Youtube is good for this), but be sure to recognize that different watches may be different, so you have to pay attention to the details. Taking a G-Shock bracelet off is quite different from taking a Rolex bracelet off, and even watches with similar designs to Rolex may be different (Rolex is very tight and you need the right tools, whereas most other watches can be done with a simple spring bar tool).

To replace a bracelet, you only really need a spring bar tool most of the time. Some use screws. Some use doubled sized screws. Some use pins. But most use springbars. But again, you have to know the details (and we can only give you more information if we know the watch and bracelet in question).