This will vary very much depending on the style of new mirror you have bought. Many simply clip over the existing mirror, making them extremely easy to install.
Others will come with their own installation kit, which may even include removing the mount of the old rear view mirror. No matter which style of install, it is generally a pretty straightforward task that won’t require too much time or a wide range of tools to be deployed.
No matter which model you select, they will all come with simple to follow installation instructions. We would strongly suggest that you read and follow those instructions!