This is a guide for setting up an Apple Mac for software development. Current versions of macOS have a fairly good default configuration for general-purpose use, but you do need to to adjust some of the security settings. In addition, you need to install several pieces of software in order to make the system useful for development.
Log in once, run Software Update, and ensure that the operating system is at the latest point release. After all of the updates have been applied, restart the computer.
Log in again and create an Admin user account for your use. If other people will be using the machine, create Standard accounts for them. Log out of the initial account, and log in to the Admin account that you have just created.
You should also find an external hard drive. Begin using Time Machine as soon as possible, as it provides the most easy method for backing up your system.